Network-wide Help Center page on Close Vote privilege says
You may cast up to 24 close votes per day (50 on Stack Overflow).
This is out of date: Ask Ubuntu, Super User, and Mathematics also have 50 CVs/day. Instead of updating this page every time another site gets more, perhaps one could say "50 on Stack Overflow and some other high-volume sites"?
(Thanks to lostsock for suggesting some)
By the way, the same page says
A closed question can be deleted as early as 48 hours after its initial closure.
which is not exactly true: it can be deleted earlier, if circumstances warrant. I don't see why this sentence is needed there at all. It seems to reassure authors that they have 48 hours prior to possible deletion, which isn't necessarily so.