The reason you see the review count even when you finish all the reviews, is because most of the reviews require more than one user to review that item in order for it to be completed, and the counter on your top bar shows the total number (for everyone). So unless you do the finishing review on an item, it will remain in the counter.
That orange notification shows everyone the same number, which is the total amount of reviews. That's why when you reviewed, the numbers didn't match up. If you are the final reviewer on a certain item, the total number will drop by one. The notification does not show when there are less than 2 total reviews.
Also see Notification for reviews shows way too much