Inaccurate Screen Time on iPhone

I’ve been checking my screen time a lot more lately and I’ve noticed something strange with my screen time. One day it said the total amount was more than 8 hours, but I know for sure I was not on my phone for that long.

My mom has now started to get mad at me for being on my phone for too long but that is not the case. I’m not sure what those gray lines mean but I’m assuming it’s contributing to the hours but I’m sleeping during those hours so I’m not sure what it’s counting.

What my theory is though is that the time where it’s saying I’m on my phone for literally over 8 hours, always happens when I shut down my phone at night when I charge it. But when I don’t charge it that’s when the screen time total seems accurate. I hope someone can explain this, it’s really annoying because i know for sure im not spending over 8 hours on my phone. Thanks for reading .

[Re-Titled by Moderator]