Not much to say about this one. Using stable channel of Chrome, Win7 64 HomePrem. Extension lists itself as v. 6.6. I’ve opened each of my messages and also selected them all and marked as read. If I disable the extension, the “1” isn’t there anymore, when I re-enable extension it comes back.
Pics with and without extension enabled:
Recently Twitch has removed the message count feature to tell you how many unread messages you have. But the feature is still in BTTV. That is why you’re experiencing a “1” next to your messages.