FaceTime on my iPad

I have a number (3) in red on my FaceTime icon on my iPad but I can't see what it's for. I've been onto my call history and no missed calls and I've now deleted all the calls made and received but the little red number is still there and I can't get rid of it. How do I do this and what was it for?

I have this happen frequently. The missed calls appear to be calls coming in on my iPhone, and then the status is 'handed off' to my iPad.

Just viewing the 'Audio' or 'Video' tab doesn't clear the notification.

I find that I have to click 'edit' then 'done' on both the Video and Audio tab, then when I return to the home screen from the FaceTime app the notification goes away.