Inaccurate screen time

is there a reason why the screen time is so inaccurate? i wish i was able to see details but obviously that's only available for pro accounts lol in last week report opal says i got a 15 hours screen time on monday???? while my apple screen time says 3 hours…i worked 8 hours and then i had classes literally no way to be 15 hours on the screen so i don't know if somehow is taking some information from my ipad or my computer where i see videos? it should only have access to my phone but since it keeps giving me inaccurate reports idk if that’s the reason