The MFD will update the display of average fuel consumption also when you are not moving, whether you are in park or drive. Essentially the MFD does take into account fuel consumed from the ICE in all conditions. Moreover, pumping to the brink or stopping at the first stop, will change the calculated percentage wrt the MFD, but it will also vary from time to time. In EU, from first stop to "full to the brink" (you see gas in the tube), is about 0.5L/0.125gal or maybe a bit more (I think it depends on how the pumps are calibrated). Over 30-35L/8-9gal, that is about a 1-2% difference. This also why likely my average is about 6-7%, instead of 5-6% - I always fill it up to the "brink", i.e. I never stop at the first stop, but add another couple.