I had this happen to me earlier today. I have a fairly new WP install, and it only has 1 custom category, which contains 3 posts.
I also have 3 static pages. And for some reason the admin panel said that ‘uncategorized’ had 3 posts (when it should of had none).
I logged into my cpanel to run phpMyAdmin to check out the database manually, and sure enough, in the table “wp_post2cat” which keeps track of which posts are in which categories. It was showing 3 posts in cat 1, which is ‘uncategorized’. Thoses posts were for my static pages. So for whatever reason my static pages showed up under ‘uncategorized’ in the sql, but the WP panel was not displaying them.. only the number.
Anyway, the moral of this story is that if you can get into your database, you can easily manually delete these ‘incorrect’ entries ??