Just my observation from owning Hondas for years it doesn't just automatically recalculate on the fly. What I mean is say I have been driving city most of the time and we go on a trip. The miles to empty will calculate on city driving so gas will "magically" appear when we stop at a rest stop. Of course there isn't a gas fairy, that just happens to be when it recalculates. The inverse happens when I go to work after a trip. I am not sure when it recalculates but these examples make it very obvious where you may not notice so much when you are using it in a routine manner.Not obsessed, just curious
If your car was going to lower its estimation of how much gas you had left at the exact time you put a gallon in there it may not register the additional gas.