Dimension area is used to design the product in the main page customify area. You can control width and height area designer product; there are five settings in here :
Using default setting: if you select “yes,” you will use the global configuration. If you use the new settings, then your product will have a different setting from others.
Widget width: we define the width area, set it to how much you want
Widget height: setting for height widget area.
Canvas area: for canvas area, you can make it full page by select 100 % or not. If you make it 100%, canvas area will cover widget area for designing product.
Top Margin: top margin is used to make a distance between canvas area and primary widget area.