From the fingers of djbob:
<djbob> for feeders (listboxes) it refers to which one they are <djbob> for any autosizing things with borders it refers to border width <djbob> for the hudicons (flag status etc) <djbob> it specifies scale <djbob> 64 * scale = final individual icon size <djbob> for quad timer + visual alerts <djbob> specifies border <djbob> for weapon switch box <djbob> specifies how much the icons are inset into their background
So for the most part it refers to border width of something with text in it, with just a few special cases as above.