Board Thread:Support Requests - Designing Your Wiki/@comment-36535642-20200701133910/@comment-168424-20200703034254

The value can be several things... tries to center the object relative to its container,  makes a space around the object equivalent to the witch of 2 'm' characters of the font,   is 6 pixels, or you can do top/right/bottom/left individual spacing like (different unit types are just for the example):

A good place to start for CSS would be Learn CSS at w3schools.com.