The place I’ve put it, on the ceiling, is where it can detect motion in the corridor but also in the stairs, as far as possible. It was my main concern : detect motion, so that I can turn the light on when someone is climbing the stairs.
I expected more, only turn it on when there is no other light or the daylight through a door is enough. But between 0 and 10 lux, 4 to 6 most of the time, the range is too small to make any sense. So I use the time of the day and the sun elevation !
I’ll be buying other motion detector from Xiaomi, I’ll try to get the first generation on sale if I can, anyway I won’t expect to use illumination sensor if I end up with a second generation !