Notification glitch?

Hi, I'm getting a sort of notification related glitch. A while ago, I noticed I had some notification that I couldn't clear. I think it was from back in June, but it just said the date of the notification(6/15/17) and nothing else aside from a blank white rectangle.

I presumed it would go away, and that the notification claiming to be unread would disappear with the "1" on my icon.

It has not. In fact, the invisible notification(I guess I'm calling it that now) went away with all notifications cleared, but it still says I have one notification left to view on my little icon. It's not a big deal, but it's a bit annoying and bothers me more than I choose to admit. Any idea what to do? I've cleared browser cache multiple times, so it might not be that. Any help would be appreciated.