No pictures as I have never done it, but logically what it is doing is saying when you tank is full but the needle shows less than full then you adjust the value from -12.8 to say -10 and watch the needle go up or maybe you have to change it to 1 or 2 etc to see the needle go up.
If the reverse is true and you have 3/4 tank full but the needle is showing full then you make it -15 and the needle will drop.
Hope that makes sense.
dont forget you also have
Modify consumption display on the FIS Screen
With this mod, you can calibrate the consumption if you see that it does not fit what you think.
1 - Module 17 - Security access (25327)
2 - Adaptation
3 - Select - Display correction of consumptions and operating range: (100%)
4 - Change the value. Default 100%
5 - The adjustment allows increments of 1%, the maximum and minimum values are 85 and 115%
Read more:
forum.obdeleven.com/thread/4199/personal-consumption-adjustment-show-fis#ixzz5NihyKFfr