Asus PG279Q not going as low at it should (height adjustement)

[Tigrou]

I have an Asus PG279Q monitor.

At the lowest setting, there is 85 mm between desk and screen border :

 

 

On the highest setting, height is 175 mm:

 

175 - 85 = 90mm

This is far from the 120mm announced from Asus (as stated in the manual)

 

Even TFT central got values differents from me  :

Quote

At its lowest setting the bottom edge of the display is 70mm from the desk surface, and once extended to maximum height it is 190mm. This gives a total 120mm adjustment range as per the spec.

 

What is weird is that if I pushed it down to the max, it seems it could go lower (but it does not) :

 

 

Same goes when going up, there is some space left in the sliding mechanism (which seems could be filled up)

 

Am I asking this because my desk is a little bit too high. I am planning to mod it (to make it lower) but gaining 15 mm (or more) from the monitor it self would be great as well.