There's a distance calibration (which you've done), and a fuel usage calibration. You should fill your tank, zero the distance, and do the fuel calibration on the next tank fill. Other factors affecting
SG mpg estimates are engine displacement, gas tank size, and cutoff. Make sure they're set up, and you've set your fuel type to hybrid if you EOC. Both
SG and UG give overly optimistic fuel usage estimates until they're fully calibrated.