Hey Db134,
Thanks for using Apple Support Communities! I understand you have some questions and concerns about the Screen Time usage information.
To start, make sure that you're not leaving your Settings open in the background when not in use, and then check if your Screen Time settings are still showing that Settings is being used as much. If so, I would like to have you turn off Screen Time, restart your device, and then enable Screen Time and test for a day to see if the same behavior continues.
You can see how to turn Screen Time on/off here: Use Screen Time on your iPhone, iPad, or iPod touch
Restarting your iPhone: Restart your iPhone
You may also want to consider updating your iOS if you haven't already done so: Update your iPhone, iPad, or iPod touch
Thanks again, and have a great day!