I agree it is confusing, I have the same.
My guess is that the 10 reviews are due to the site self evaluation. You have already done them, but the questions are still open to review by others.
The extra two come probably from close/reopen votes or suggested edits already reviewed by you, but not by a sufficient number of people to be actioned by the ...
Once you graduate from reviewing suggested edits to being able to review items in other queues, the meaning of that number changes. It no longer represents the number of suggested edits you can review, but is a number that is vaguely related to the total number of items that could potentially be reviewed by somebody. Apparently, this is by design.
This looks like a bug to me too.
I completed reviewing the site self-evaluation as well, and my toolbar still shows them as awaiting my review. When I click on it, the review queue is empty.
Marking it as status-reproduced so that someone can take a look at it.