Advanced users of this valve can make upgrade to control valve position without any temperature calibrations.
You can solder fixed resistor instead of NTC and then set target temperature to change valve position to desired value. If X is your target temperature then valve position will set according to actual temperature Y:
Y=X+1: position - 100%
Y=X: position - 90%
Y=X-1: position - 80%
…
Y=Х-8: position - 10%
Y=X-9: position - 0%
So you can fix Y with certain resistor (say 10k for 25 degrees) and then set position indirectly - by setting target temperature different from this fixed value for several degrees. Without any calibration. And you will be sure that your valve position is set to your desired value without any fluctuation for internal temperature sensor.