I've was given the access moderator tools privilege (on Astronomy SE, not Meta) and I've found the review count keeps increasing.
I've cleared outstanding tasks on my list a couple of time now, but the count display (orange box, white number) keeps going up and when I click it after clearing tasks there is nothing to do (the detailed review and tools page shows zero counts).
I cannot find an explanation for this, so I'm presuming it's a bug, but maybe some of you know if it is or is not.
I note this has occurred elsewhere on SE but also on a Beta site. So this seems to be a Beta site issue. As it was referred to as being related to caching perhaps it's as simple as Beta sites not having caches updated as frequently.