Please explain the Screen Time math

Yesterday my son was using his computer for far longer than appropriate and we've been having issues with settings getting changed and whatnot. However, he'd had his computer taken away and it was sitting in my trunk for the past few weeks.

I went to check on his usage to see if the App Limits had been removed and, as you can see, they had not - he was allocated 30m on Roblox, 30m for chess and 30m for YouTube and browsers. Somehow, the system recorded 6+hrs of usage (I'm pretty sure this is accurate), but it also shows an average of 23+h. This cannot be.

What is going on? This is unusable if I cannot rely on it to do the job it was set out to do.