Today, I did 20 reviews in the Suggested Edits queue on Stack Overflow. However, one of the edit suggestions was to a post that was removed shortly after.
I'd expected that the used slot would come free; it's happened before and is how this is supposed to work. Looking at the SE Review Queue stats, another reviewer did get 21 reviews today, so it seems this rule hasn't changed.
So I'm wondering - where's my extra slot?
The user with 21 reviews also reviewed an edit to their own post, which is an exception to the 20-reviews rule.