I have noticed that there has to be some kind of gain on review quotas. I remember having my daily limit on First Questions being 40, but today when I did some reviewing, I saw that my daily limit has increased to 80.
Does it increase by the number of reviews you have done or by the queue size?
I'm a little skeptical if it is the number of reviews waiting in the queue because at the moment it was +10k which is pretty normal, I believe.