I use mine, though sparingly. I set the minimum at '0' instead of a negative value.
I set the maximum at full value on 'User' setting, but had to use a lower setting when on 'Standard' to avoid luminance clipping.
Setting the minimum below '0' results in muddying of the picture with inadequate 'drive' or contrast.
Mine is quite sensitive, but a room light is not nearly as powerful as daylight -- why do you want it to react to low-level light?
The purpose is to adjust the picture to the surroundings. A simple lamp is not going to make your eyes perceive the screen more dimly,
so the screen doesn't need to compensate for it. Have you tried different values of minimum and maximum? Also, shut off the visual display
and let your perception be the judge rather than the number of leaves displayed. That might be your problem right there.
Maybe you got a set with a faulty photometer? I doubt it...