I've noticed similar Screen Time reporting inconsistencies on my iPhone too — it often seems to round up or double-count time spent in certain apps. From what I've read, this can happen when background app refresh or certain system processes are running alongside the app you're actively using. The system sometimes aggregates background activity into the total, making it look like you spent more time than you actually did.
One thing that helped me was going to Settings > Screen Time > See All Activity and then toggling off "Share Across Devices" temporarily, waiting a few minutes, and turning it back on. It seemed to resync the data and make the reporting more accurate. Also, checking that date and time are set to "Set Automatically" can help since manual time adjustments sometimes confuse the tracking.
If you're testing different apps and want to track usage more accurately, I've found that using a reliable tool for monitoring app performance can give you a clearer picture of what's actually running in the background. Hope this helps — let me know if the reset steps work for you!