Free space mismatch in iOS 11

[Finnfire]

Hello everyone! This is my first post, and I'll try to keep it short and to the point

I checked the free space on my iPhone 5s using both Settings > General > iPhone Storage and System Status (by Jiri Techet) -

• iPhone Storage reports ~6.5GB free space (General > About is more precise - 6.49GB)
• System Status reports ~4.9GB free space.

This is a large discrepancy - any idea why such a difference?

TIA,

Steve