iPhone Storage Discrepancies

I deleted an app (video editing) that held 10 GB. But before deleting, I tried erasing most of the files I had on the app to see if it would make a difference on my storage in the Settings app. It did not. It remained to hold 10 GB even though I deleted a majority of the files on the app. So I decided to delete said app from the Settings app, thinking I would be free of 10 GB from my storage. I was not. Upon deleting the app, it increased my storage space by 2 GB only.

I also calculated all of the storage values that each app held, you know the numbers we're shown on the Settings app? And I got a total of 106.5 GB. But according to Settings, I had 123.2 GB of 128 GB used.

How do I fix this?