How do I ensure accurate Screen Time tracking on my iPhone?

Why are there grey bars all over my screen time? My screen time says I used my phone for 9 hrs 30 mins on Saturday, which includes grey bars showing it being used from midnight to 6am, when I was asleep with the phone on the bedside table. Why have Apple allowed such a huge bug into their screentime feature, and how do I stop it doing this so I can know my real screentime?

[Re-Titled By Moderator]