From the higher point to the lower, I think there is about 300µm.
With a ruler the bed looks like perfectly flat, it is a bit tilted due to the 3 lead screws which use only one motor and belt and should be leveled by hand, see : Manual Bed Leveling / Manual Bed Tramming | Bambu Lab Wiki
Note that I get different results depending on the PEI plate and how I set it in place.
Overall I will say I have a maximum of 100µm/150µm of real deviation/warping depending on plate, (not counting tilting)