although the meter is back in the system, the gas is measured at the nozzle. What is in the hose is taken into account when weight and measures checks the pump. 100 cu. in under and 200 cu in. over in a 100 gallons. Your gallon jug most likley wasn't a calibrated vessel.. The temp. has to be the same when both measurments are made. They don't fill milk jugs to the top to get the gallon, they are down an inch or two. Those hose drainers are stealing gas from the next guy!!!