The easiest way is to use examples that demonstrate the different ways to use the so-called ‘checkpoints’.
The indicator light shows low residue. Driver added a record of refueling, introduced mileage, date and checks ‘checkpoint’. In the vehicle settings of the application the residue volume has been specified with 3 liters. The program knows that the tank contains about 3 liters at this checkpoint.
The car has a problem – the fuel level is not shown. But the engine begins to run poorly and makes a noise when the tank gauge is at a quarter. This is checkpoint time – the driver has to supply the remaining fuel in the tank at such symptoms and not to forget to mark the new record as a “checkpoint”.
Even a full tank can be called “checkpoint” – the principle does not change – it is an artificially detectable residue in the tank. The reliability depends on many factors – weather, position of the car, precision eye and ear of the driver. This method of indicating the remaining fuel in the tank is possible, but not recommended because of the greater uncertainty compared with using the “full tank” method.