[1.08.03b]Possible Aircraft Fuelcost issue

[zgrssd]

Trying to figure out some parts of the Plane formula, I noticed a oddity:
Both my starting fighter and my starting scout have a Range of 11 hexes.
For a fighter the stated Fuel/hex is 2.8
However the "Move Oil" under Managemnet -> Model -> Op. Cost says 28 - 2.8 times 10, not 11.
The Scoutplane follows this trend that "Move Oil" = Fuel/Hex * (Hex Distance -1)

This seems off.