#kboard-thumbnail-list .kboard-list.record ul.kboard_record_ul>li 부분이 style.css에 두번 정의되어있던데..

kboard/스킨/해당스킨/style.css 에 정의되어 있는 #kboard-thumbnail-list .kboard-list.record ul.kboard_record_ul>li를 삭제하시거나 !important 옵션을 쓰세요

bridge-child 라는 테마 style.css에 정의를 하셨네요..

※ bridge-child 테마 style.css 보다 kboard skin style.css 가 나중에 로드되어서 width 49% margin 2% 가 적용되고 있습니다.

근데 말씀해주신대로

#kboard-thumbnail-list .kboard-list.record ul.kboard_record_ul>li { float: left; width: 48%; margin-right: 1%; margin-bottom: 2%; list-style: none; background-color: #fff; border: 1px solid #d7d9dd; }

수정후

style.css 맨 밑에 복사해서붙였는데

아무런 반응이 없네요

참고로 style.css 전체소스 첨부합니다

-==============

/*
Theme Name: Bridge Child
Theme URI: http://demo.qodeinteractive.com/bridge/
Description: A child theme of Bridge Theme
Author: Qode Interactive
Author URI: http://www.qodethemes.com/
Version: 1.0.0
Template: bridge
*/
@import url("../bridge/style.css");
@import url(http://fonts.googleapis.com/earlyaccess/nanumgothic.css);
@import url(http://fonts.googleapis.com/earlyaccess/nanummyeongjo.css);
html,body,body *{font-family: 'Nanum Gothic', sans-serif;}
/*--------------------------
Reset
--------------------------*/
ul,ol,li,dl,dt,dd{margin:0; padding: 0;}
em{font-style: normal;}
/*--------------------------
Font / Color 
--------------------------*/
.wpb_wrapper>p{line-height:1.4;}
.fz15{font-size: 15px;}
.fz16{font-size:16px;}
.fz17{font-size:17px;}
.fz18{font-size:18px;}
.fz19{font-size:19px;}
.fz20{font-size: 20px;}
.fz21{font-size:21px;}
.fz23{font-size: 23px;}
.fz24{font-size: 24px;}
.fz25{font-size:25px;}
.fz26{font-size: 26px;}
.fz29{font-size: 29px;}
.fz30{font-size: 30px;}
.fz31{font-size: 31px;}
.fz34{font-size:34px;}
.fz36{font-size: 36px;}
.fz48{font-size:48px;}
.fz50{font-size:50px;}
.white{color:#fff;}
.white p{color:#fff;}
.blue p{color:#325a9d;}
span.blue{color:#325a9d;}
span.green{color:#4d9904;}
.violet p{color:#4e55a6;}
.black{color:#000;}
.c46 p{color:#464646;}
a{color: inherit;}
a:hover, a:link, a:visited{color: inherit; text-decoration:none;}
.padding_y10{padding: 10px 0;}
.tacenter{text-align:center;margin:0 auto;}
.bold{font-weight:700;}
.uppercase{text-transform: uppercase;}
.bluebg{background-color:#325a9d;padding: 7px 14px;}
.footer_bottom{font-size:13px;color:#9e9e9f;}
.dib{display: inline-block;}
.bullet{background-image:url(images/bullet.jpg);background-repeat:no-repeat; background-position:0 5px;padding-left: 23px;}
.content .container .container_inner.default_template_holder, .content .container .container_inner.page_container_inner{padding-top: 40px;padding-bottom: 40px;}
.graybg{background-color:#5b6474;}
.bluebgc{background-color:#325a9d;}
.violetbgc{background-color:#4e55a6;}
.w95{width: 95px;}
.h95{height: 95px;}
.circle{display:table;border-radius: 50%;vertical-align:middle;padding: 0;}
.w95.h95.circle p{display:table-cell;vertical-align:middle;width: 95px;height: 95px;}
.fz16 dl>dt{margin-right: 14px;}
.fz16 dl>dt, .fz16 dl>dd{float: left;}
.fz16 dl{border-bottom: 1px solid #dfe1e4;padding: 25px 0;}
.fz16 dl:after{display: block; clear:both; content:'';}
/*--------------------------
Content
--------------------------*/
.wpb_text_column dl.sub_dl{text-align:center;margin-top: 35px;margin-bottom: 50px;}
.wpb_text_column dl.sub_dl dt{font-size:30px;color:#333;letter-spacing: -1px;margin-bottom: 15px;}
.wpb_text_column dl.sub_dl dt>em{color:#a4aab7;}
.wpb_text_column dl.sub_dl dd{font-size:18px;color:#333;}
table{width: 100%;word-break:break-all;}
table.table-1 tr:first-child{border: 2px solid #325a9d;}
table.table-1 tr th{font-size: 16px;color:#000000;font-weight:700;text-align:center;}
table.table-1 tr td{font-size:14px;color:#333333;padding:15px;border-width: 0 1px 1px 0;border-color:#d2d3d5;border-style: solid;text-align:left;letter-spacing: -1px;}
table.table-1 tr td:first-child{width: 135px;text-align:center;}
table.table-1 tr td:first-child ~ td{vertical-align:middle;}
table.table-1 tr td:last-child{border-right: 0;}
table.table-1 table{table-layout: fixed;}
table.table-1 table tr:first-child{border: 0;}
table.table-1 table th{width: auto !important;color:#fff;background-color:#8f9db7;}
table.table-1 table td{padding: 5px 0;text-align:center;}
table.table-1 table th{font-size:14px;padding: 0;}
table.table-1 tr th:first-child{width: 100px;}
div.table-2 table{table-layout: fixed;}
div.table-2 table thead tr th{font-size:15px;color:#fff;background-color:#43659d;text-align:center;padding: 10px 0;}
div.table-2 table tbody tr th{font-size:15px;font-weight:700;background-color:#e9eaed;text-align:center;border-width: 0 1px 1px 0;border-color:#d2d3d5;border-style: solid;padding: 10px 0;}
div.table-2 table tbody tr td{font-size:15px;text-align:center;border-width: 0 1px 1px 0;border-color:#d2d3d5;border-style: solid;padding: 10px 0;}
div.table-2 table tbody tr th:last-child,
div.table-2 table tbody tr td:last-child{border-right: 0;}
.wpb_widgetised_column.wpb_content_element .widget.widget_nav_menu ul:after{display:block;clear:both;content:'';}
.wpb_widgetised_column.wpb_content_element .widget.widget_nav_menu ul li{float: left;width: 50%;}
.wpb_widgetised_column.wpb_content_element .widget.widget_nav_menu ul li a{display: block;padding:10px 0;font-size:16px;color:#535e6e;font-weight:700;border-width: 1px 1px 1px 0;
border-style:solid; border-color: #8895b5;text-align:center;}
.wpb_widgetised_column.wpb_content_element .widget.widget_nav_menu ul li:first-child a{border-left: 1px solid #8895b5;}
.wpb_widgetised_column.wpb_content_element .widget.widget_nav_menu ul li.current-menu-item.current_page_item a{background-color:#2c3d6a;color:#fff;}
aside.sidebar{border: 1px solid #a6b6c1;}
aside.sidebar .widget.widget_nav_menu ul li{text-align:right;}
aside.sidebar .widget.widget_nav_menu ul li a{display: block;font-size:15px;color:#333333;text-align:right;padding-right: 20px;}
aside.sidebar .widget.widget_nav_menu ul:first-child>li>a{padding-top: 10px;padding-bottom: 10px;border-bottom: 1px solid #a6b6c1;}
aside.sidebar .widget.widget_nav_menu ul:first-child>li:last-child>a{border-bottom: 0;}
aside.sidebar .widget.widget_nav_menu ul:first-child>li{margin-bottom:0;}
aside.sidebar .widget.widget_nav_menu ul ul{margin: 0;padding: 20px 0;background-color:#ecf0f3;}
aside.sidebar .widget.widget_nav_menu ul ul li{margin-bottom: 10px;}
aside.sidebar .widget.widget_nav_menu ul ul li a{font-size:14px;}

aside.sidebar .widget.widget_nav_menu ul:first-child>li.current-menu-item.current_page_item.current-menu-ancestor.current-menu-parent.current_page_parent.current_page_ancestor>a{color:#fff;background-color:#243d64;}
aside.sidebar .widget.widget_nav_menu ul:first-child>li.current-menu-ancestor.current-menu-parent.current_page_parent.current_page_ancestor>a{color:#fff;background-color:#243d64;}
aside.sidebar .widget.widget_nav_menu ul ul li.current-menu-item.current_page_item a{display: inline-block;position:relative;color:#fff;background-color:#243d64;}
aside.sidebar .widget.widget_nav_menu ul ul li.current-menu-item.current_page_item a:before {content: '■';color: #fff;font-size: 5px;padding: 10px;position: relative;top: -2px;left: 4px;}
aside .widget{margin-bottom:0;}
.mobile_menu_button span{color:#fff;}
@media only screen and (max-width: 1000px){
.header_bottom {
    background-color: #252525 !important;
    padding: 0;
}
}

nav.main_menu > ul > li > a:hover span{background-color:#325a9d;}
ul.location_ul {padding: 0;}
ul.location_ul li{list-style: none;margin-bottom: 5px;font-size:16px;}

nav.mobile_menu ul li a{font-size:15px; padding-left: 20px;}

@media only screen and (max-width: 567px){
.carousel:not(.advanced_responsiveness) .carousel-inner h2 span{font-size:28px !important;}
.carousel:not(.advanced_responsiveness) .carousel-inner .q_slide_subtitle span{font-size:16px !important;}
.content .container .container_inner.default_template_holder, .content .container .container_inner.page_container_inner{padding-top: 45px !important;}
aside.sidebar{margin-bottom: 30px;}
.container_inner{width: 340px;}
body.page.page-id-8 .wpb_text_column.wpb_content_element.fz18.tacenter,
body.page.page-id-8 .wpb_text_column.wpb_content_element.fz18.center{margin-bottom:20px !important;}
body.page.page-id-8 .wpb_text_column.wpb_content_element.fz21.tacenter{font-size:16px;}
body.page.page-id-8 .wpb_text_column.wpb_content_element.fz25.bold.tacenter{margin-top: 20px !important;}
.wpb_text_column.wpb_content_element.fz36.bold.tacenter{font-size:24px;}
body.page.page-id-8 .separator.transparent{display: none;}
.footer_bottom{line-height:1.4em;}
table.table-1 tr th:first-child{width: 15%;}
table.table-1 tr th:first-child + th{width: 42.5%;}
table.table-1 tr th:first-child + th + th{width: 42.5%;}
}

select.family{width: auto;background-color:#000;padding: 10px 0;}
select.family, select.family option{font-size:14px;color:#909090;}

#kboard-default-rnd-list .kboard-header {
    display: none;
}

#kboard-thumbnail-list .kboard-list.record ul.kboard_record_ul>li { float: left; width: 48%; margin-bottom: 1%; list-style: none; background-color: #fff; border: 1px solid #d7d9dd; }

위 속성이 적용되어 있는걸 확인했습니다.

width가 49%로 적용되어 있고, margin-right가 2%라서 합이 51%라서 다음줄로 넘거가는 겁니다.

width 값을 줄이거나 margin-right 값을 줄여보세요~