To get a more accurate representation of your actual use you should go to the last 10 days view and click on a single day which accounts from 12:00am-12:00am. 24 hours.
So since I went to bed before midnight and didn’t use my phone till I took it off at 9:55am my usage doesn’t start until 9:55am and it ends at 12:00am that night. My screen on usage was 3hr 8m that day. Ended with 29% on my iPhone 7.
With the last 24 hour view that you have there it’s bleeding together usage from the previous day. So it’s just not an accurate picture from the last charge.