I would think it should be like calibrating the mpguino
Mpguino calibration - EcoModder
basically you fill it up, do a tank reset on the supermid and on the instrument panel (or note the mileage) drive a couple hundred miles, replicate the fillup conditions and see how many miles the odo says and how many gallons the pump says and how many miles and gallons the supermid says.
then adjust the fuel parameter up or down by the percentage that it was off
ditto for the miles (distance parameter).
review the mpguino calibration link to see if this makes sense, but you will have to convert the supermid numbers to english of course.