clearing allegedly unread messages on Mac

OK, I regularly see, when I hold down the mouse button on the Messages app in the dock, messages that are allegedly not read. As in "74454 (1 unread), 22995 (1 unread)". Goodness knows what those numbers are, but I have NO unread messages. So how do I make those seemingly permanent unread message notifications go away. LOTS of people complaining about this, and NONE of the suggested fixes actually works. I think that if I reboot, they will go away, but geez, why should I have to do that???