The fuel computer resets every time you stop the engine. The "distance to run" is therefore highly unreliable.
As soon as I see the last block flashing, i set my trip meter to zero.
If I'm cruising, it reads very closely to the fuel computer. e.g. the fuel computer usually counts down from 95 and I note that as it gets to say, 20, my trip meter will say about 75.
I reckon on 85 kays out of a flashing low level light, when cruising. Around town it might only be 60 or even less.
Trust the trip meter!