At one particular destination of our airline we always have a fuel difference of over 100kg between the amount re-fueled counted by the fuel truck (in liters) and the amount calculated by subtracting fuel remaining before refueling from ramp fuel after refueling.
This problem always happens at the same airport, on all aircraft. Compared to other airports, such a calculation gives an average difference of 30 kilograms.
It must be an S.G. problem. The source may hydrotreat their kero as opposed to just merox treat it which results in a slightly lower SG and therefore less mass for the same volume.