Well, there is a difference between how linear the blocks fade away vs the bike's computer figuring your average mpg gallon usage for you
It's simple if you fill up the same way every time to the same fill point in the neck every time to to calculate what your gas mileage is by miles ridden divided by gallons to refill. 175 miles ridden divided by 3.8 gallons to refill will net you 46 mpg, regardless of what the computer says (I like simple math). 175 miles ridden divided by 5.0 gallons to refill nets you 35 mpg, regardless of what the computer says. And it doesn't matter if you rode easy some, hard, some, point and shoot in the twisties some, ran into a headwind or a tail wind some, it's an average. Math is math. Over that 175 miles you averaged X mpg for the whole 175 miles depending on how many gallons it took to refill.
The disappearing blocks are just there to drive you crazy and make you nervous about running out of fuel. The computer is just hand grenades and horse shoes close.
2018 Yamaha FJR 1300A
2014 Honda CB1100 DLX
It doesn't matter what I ride, where I ride, how fast I ride, or how far I ride... it only matters THAT I RIDE...EVERY DAY. "Ferret"