GEAR FOR CALIBRATION

Hi all,

Can someone explain with which gear i should calibrate Tacx Flux S?  I try to explain better:

Each time i start a ride, the app asks to calibrate the trainer. I usualy put 50x11 reaching the speed required. The problem is that even if i start with a descend of 15% it seems i am pushing a 80x11. 

This causes i have a lower gear ratio for the climbs and honestly it is difficult to understand when i can push or not

Can someone help me on this? 

There is one gear ratio that could be fine to make the ride most real ?

Thank you all, really