My PM alert at the top right shows I have -2 new messages. What is that?

It's a glitch from the last update. When you have a new message, it shows "1" or whatever you've got waiting. When you read it, it goes to "0". When you delete it, it subtracts 1 and shows "-1" (or 2, 3, etc). It's nothing to worry about, but looks quite odd. I'm hoping they'll have a patch soon.

Ok, it just kind of showed up for me yesterday and I had not deleted anything just sent out one message. I did delete some after I saw the -2 but that made no change to the number.