I've been digging around in Theme London Fixed, and came around a strange bit of CSS I don't understand the intent behind.

Hi Alexandre,

Well spotted. Grids are used to align things on the page. You have columns, to size things, and gutters to space them. Because you can't have margins between cells, the gutter size (usually 20px) is added to the column size, and a padding right with that same size is also added. This was used by EditRecords and SowRecords for the caption size (Now that we have the Form widget that's based on containers, that is not so much needed).

Cheers,
Tiago Simões