Hi
It due to the style of this module only, the 6th items in module will have that style.
If you don't want it, open the file:
root/templates/ja_comics/html/mod_articles_category/style-2.php
Line 50:
<div class="item-inner <?php echo ($i==5) ? 'item-view-vertical-2' : 'align-meta-bottom' ;?> bg-<?php echo $catclass ;?>">
change to:
<div class="item-inner align-meta-bottom bg-<?php echo $catclass ;?>">