New message notification in system tray doesn't reflect new messages in inbox

The new message notification in the system tray mentions new messages (for my IMAP account), but there are actually no new messages in the IMAP account inbox. The system tray notification goes away if I click on another mail account and then back on my IMAP inbox.

I have a number of filters configured to move messages to folders if that counts. I would expect the system tray notification to reflect new messages in my IMAP inbox but this doesn't always seem to be accurate. As an example, when I hover over the system tray notification, it will say "3 new messages for name@domain.com" but when I go to my inbox there aren't any unread messages for this account's inbox.