High screen time

hello, i got 7 hours on iphone 13 but i was like 30 minutes becouse i was in school. before i go to school i closed every app and turn off mobile after i turn it on it shows me 7 hours but i wasn’t. screen time showing me I was only on the apps for a total of 30 minutes but the graph shows me 7 hours. i have iphone 13 and ios 18.1. anyone help please (sorry for bad english im not from here)