Actually ZF6 indicates a change of 4 to 5 lux.
@_jis_ thanks for the input! This tells me that the problem is specific to my device where the value changes directly from 0 to 7. I'm not sure how to fix it, one thing I can do is to hard reset my phone because I've never had to do that before (something I like about this device).
It could be useful to get a confirmation from another person before I try a hard reset. Or to know if different models of the ZF6 use different sensor suppliers.
For me AIDA64 give only 0 7 15 23 31 47 55 63 71 79 87 inside a room with artificial light. During one second the value can change from 0 to 7 or 15 or every combination of those 3 numbers like 20 times. The odd thing is that the 0 value appears also when in the room there is the light on, only by pointing in a direction different from the position of the light.
@ghiani.riccardo what you described is exactly the same on my side! Let's try to maintain a productive conversation though, I'm sure the mods are doing their best to help us. I'm trying to focus on finding the root cause because this issue could have a very simple fix, but let's try to find the underlying issue first.