Displacement Value

I have generated displacement mask map but How to know how much surface is displaced?

What is max and min displacement after this image processed?

The value of the pixels is the displacement. But it can be affected by atmospheric disturbance, so comparing results of different pairs helps to identity the true patterns.
Please also note that the extreme values are often not correct nor representative, because they are likely to be caused by unwrapping errors in areas of low coherence.