I asked the same on their Facebook but no answer.
Measured in my gym at a day it was AQI 500. Got the value 1600 on my meter when outside it showed 16000! on the pm 2.5 scale.
In my apartment I had 100-150 with purifiers on.
My gym is located underground -1 floor.
Many people, heat, movement etc will affect the meter
Will do a test today when the air is good