Yes, how else do you think that the Stack knows how much fuel is in the car ?

You have to remember that the float that is connected to the gauge just gives off a voltage signal from 0-5 which is then interpretted by the fuel gauge as to what position it is in and how that equates to fuel quantity. As the Stack is more accurate, you have ten measuring points to program in, which it will then extrapolate between to give a precise figure in litres (rather than just full, ¾ full, ½ full, ¼ full and empty). This means that you have to do the process above, so that the Stack knows what position the float is in. Obviously it is individual car dependent, as the float gets moved when the fuel pumps are changed, so Ben's figures might be close, but they won't be accurate.