Checked the iPhone 7 with iOS12 - is of 22, 67, so that seems to be true
burnice answered on June 3rd 19 at 19:45
Looked, system for iPhone 7 32GB: 6.34 GB)))
Actually had the same joke on the previous iPhone 5 16GB, literally forever was the free 500 megabytes and always had to take a haircut, decided when I sold it and made a system reset, just Bang, plus 7-9 GB in the process any upgrades, etc. iPhone bad cleans resources.
Solution: make a backup through itunes on the PC and restore from it from a dozen other GB added.