Those who have upgraded to Review Board 1.6.0 have no doubt noticed some problems with a few of the counters on the side of the Dashboard. Several may be set to 0, or in the negatives. This is an annoying bug, and many have reported it to us.
Don't worry, though, we were prepared for such things! You can reset your counters by typing:
rb-site manage /path/to/site fixreviewcounts
The counters should fix themselves the next time you're signed on. Now, any users who haven't logged in since the upgrade may find themselves hitting this bug again. Just re-run the same command and it'll solve it.
The upcoming 1.6.1 release will fix the bug and will perform a counter reset on your install. This should take care of it for everybody. You can expect that this weekend.