Your current trip distance far exceeds the average entry. This fuel-up will be saved as a missed fuel-up
This has suddenly started appearing on the app after the last update even though I haven't missed any fuel-ups and there is nothing out of the ordinary on my numbers. I tried deleting all my fuel-ups and re-entering them and it did the same again. And again. It will not let me reset the missed fuel-up flag either. (I have it set to enter trip distance btw)
There is not a bug, but an oversight in functionality that has caused this. The update to allow you to ignore the missed or partial fuelup suggestion is currently under review by Apple. It should be released to iTunes later today.