I f you want to know you have been under-dispensed in the fuel filling station.
Whenever you are at the petrol station, as the attendant start to dispense the fuel the litter reading will not start from zero it either start from 0.2 or 0.3 that means they are taking 20% or 30% of a liter from every liter you buy.
But if the liter reading starts from zero then the station is giving you 100% of what you are buying. But this can only happen in few NNPC stations.