I realize this thread is very
Posting this anyways though because it worked for me (mine was showing 65532 messages unread, then 0, then back to 65532) and I was almost going to post my own thread asking WTH?, but found this one.
After a little Google searching, this fix seems to have worked.
Go to your inbox and select all of your messages.
Scroll down to the bottom of the page to the 'move to' folder and select "mark as read" and click "Go."
Should show 0 unread messages.
Even if your messages are already read, this works. Weird.