Hello,
I found out that when using a high ISO the value reported by the phone is quite wrong.
As a test I took a photo in the same lightning environment using the phone and a mirrorless camera Sony A7 III.
phone f1.9, 0.5s, 6400ISO
sony A7 III f2.0, 0.5s, 6400ISO
sony A7 III f2.0, 0.5s...