User blog comment:Rupert Giles/Layout Changes: Breakpoints and Typography/@comment-4189499-20150520014724/@comment-452-20150520030436

That image indeed shows a content space width of 1064px, but because the width of the browser is higher than 1575px, it's supposed to have a content space width of 1238px.

Wikia Staff, please confirm why this is occurring, and whether it's intended?