Huge value on Intensity minutes

Strange, indeed. Should be exactly 803. What does the detailed page show (when you tap on the intensity minutes pane)? Did you try forcing the activity to stop, and relaunching it?  Or perhaps the weeks are pretty long in Finland, in the last time, aren't they?

Yeah, was indeed  strange but it was gone just how like it came - out of nowhere. I reopened the app and - lo and behold - it was just right again. It must been temporary glitch. Still, this topic is here to gather other occurrences from others if the clich is any common at all. 

... and it was right on detail page of the activity minutes. 

This phenomenon keeps popping up every now and then. Usually goes away after a while. At least once I just before sync my 935 with Garmin Explorer, it may be related or not. 

The extreme value usually is Intensity Minutes but sometimes it has been Steps.