Even if it’s completed shows, I’ve been using this tracker for about 3-4 months if not more, and I watch anime everyday .
I also update my account episodes on this tracker everyday.
Ah, now I see what you’re confused about. See, this number doesn’t show the number of days when you watched anime. It shows your total watch time by summing up the lengths of every anime episode you have watched. So in other words, it shows how many days you would have spent watching anime if you would have watched all those episodes non stop ;-)