I've got an '05 MT HCH and the display jumps in 3 or 4 tenths at a time. I can't verify the 49.9 to 50.3 jump because my lowest displayed mileage after 3 tanks is 57.9. The next jump after 57.9 is 58.2.

I love the car overall but the display should update in single tenths and should refresh a bit quicker IMO.