Look at the number of notifications. What do you see? - Yes, there is -10.
As it turns out, if you very fast click on -
Even if you simply click on a few laps they stray from the correct number.
The unread page works well if the # of new posts per visit is fewer than 10. After that it gets a bit hard to keep up
Some newer changes may make the list a little more manageable.
/cc @psychobunny @baris