over-calculating

a) Spending time calculating a value with way more significant figures than akcually required, b) Calculating something that shouldn't be calculated, e.g. time "wasted" whilst you're reprimanded by parents for your trivial wrong-doings when you ought to have that time to catch up latest YouTube videos

I spent an hour over-calculating how much time I'd lose getting yelled at for missing curfew, when I could've just been watching my favorite YouTube videos instead!