Not sure if that's a bug or a feature, but I'll share it with you:
I still have some unread notifications, however, the counter at my avatar vanished.
I would have expected it to show me thenumber of unread notificationsI have.
It could be feature, to only display "new" notifications (since my last visit to the notifications-area); when I started today, I had the counter on 5, then I visited my Notifications. I read some of them, but not all.