The builder themes are based on the Foundation front-end framework.
The Foundation grid system consist of 12 columns. Width of each column is specified in/by the small-#, medium-#, and large-# classes.
<div class="row"> <div class="small-2 large-4 columns">...</div> <div class="small-4 large-4 columns">...</div> <div class="small-6 large-4 columns">...</div> </div> <div class="row"> <div class="large-3 columns">...</div> <div class="large-6 columns">...</div> <div class="large-3 columns">...</div> </div> <div class="row"> <div class="small-6 large-2 columns">...</div> <div class="small-6 large-8 columns">...</div> <div class="small-12 large-2 columns">...</div> </div>
If you need more information about the Foundation grid system, please visit the official foundation documentation.