Does the consumption indicator in the G serve only to calm your conscience?

Hello. That there is no indication of instant consumption in the G is understandable given the fuel consumption. Anyone who buys a G knows that this is not a consumption-optimized vehicle. But is it normal that the average consumption indicator is completely wrong? What do you have here for experience? With my other vehicles there is a tolerance of up to 0.7 liters. With the G 350 BT (model 2015, recently purchased) I now had an average consumption of 11.4 liters after 602 KM / 100 KM on the display. I have now refuelled 77.77 liters. This results in an average consumption of 12.92 liters / 100 KM (of course the refueling method is also inaccurate, the tank quantity depends, among other things, on the outside temperature and on the previous even refuelling; but certainly more accurate than the display). Clearly 12.92 liters is fully in the bearable range, especially with a diesel engine not yet in use, many short distances, preheating (about 20 minutes) and a G Untested drivers. But you can’t rely on the display. This is 1.5 liters next to it. That’s a considerable deviation. Does the display only show desired values and serve to calm your conscience? Will this be better during G life or should you simply hide the display in the future? Or does the heater consume a huge amount of fuel (it could actually only make up half a liter for the total quantity of fuel used and it would be cleaned up around the heating system. still use 12.8 liters). Greetings Tom