In my inbox there are 4 unread messages (notifications from redmine) that are not visible in unread filter. As you can see in the video below there should be 10 unread messages shown with this filter. Those notifications are missing.
I have two unread messages on Arch Linux, and they only started appearing with 1.5.4. They don’t appear anywhere in the listing, and when I log into Gmail’s web site, they don’t appear there, either.