PC says my storage is smaller available than iTunes and my iOS

Hi there, my iPhone 6S' about is saying that I have availability at 74.48 out of 128 GB

However, my laptop is saying the internal storage (mainly DCIM) has only 49 out of 119 GB available.

This makes no sense to me as I have reset my phone as I read that it could be my phone but the storage seems to be fine. Any ideas as this mismatch is making me worried about how much footage I can shoot for my vlog. Thanks!