Why iOS settings and iTunes report the storage usage differently? My iTunes shows me that there is about 7 GB of free space, while iOS settings shows me that there is only about 80 MB of available space.  How do free space and available space differ?




Additional note: I tried to sum all used sizes of apps in Manage Storage list; its total (about 2925 MB) does not match to iOS settings’ Used size report (11.7 GB), but match to iTunes’ storage usage chart.
I reset my iPhone and recover the backup data.  My all installed apps and data are seemingly maintained well, but its storage usage became changed: about 7 GB of new free space came out.  Also, it’s reported in the same way by both iTunes and iOS settings.

I’m still not aware of the cause, but my problem was anyway solved.