OP; I'm also surprised that anyone with a new car would play 'Russian roulette' with the fuel gauge and 'miles left to empty' range indicator, when they've had the car less than a month so are unlikely to know how accurate the gauge/indicator are. If fact you've said earlier in this thread that 0 miles may mean 0 miles - which was displayed before you reached your destination - and that you wouldn't want to run out of fuel;
A car such as a Golf GTI performance is a great car and one to be driven and enjoyed, not spend hours or days arguing about discussing what in my opinion is a first world problem. My solution;
- fuel gauge drops to 1/4 full; go and refuel to eliminate the risk of running out of fuel
- if you think the fuel retailer's pumps might be reading the incorrect amount of fuel dispensed; use a different filling station
Doesn't answer your original question, but as I've said, first world problem, and there are far more important things to spend time on.
Has this thread now run it's course?................probably not 
As this is my third Golf and our other car is VAG - I really did not know I was playing "Russian Roulette." Like I said - I was shocked when I saw how much fuel went into the car. Hence this thread on a "GolfGTIforum".
After reading the "GolfGTIforum" I decide that it might be best to use Super Unleaded in my car. My local garage charges £1.32 for it. Sainsburys as you can see on my receipt was much cheaper. Given my previous experience of VAG cars, I did not consider for 1 second that I was taking a chance. Like I said I was shocked.
It would be nice to be able to drive my car all day long. However, that is just not practical. Sharing experience, opinions and knowledge on the "GolfGTIforum" with other owners and enthusiasts, is
usually a pleasant way of passing the time until my next drive.
As for this thread - well I was looking for some answers. Unfortunately, it appears as if no one is able to help.
I understand other people don't care why my car appears to have no 'extra' fuel reserve, but I do. It would bug me not knowing. That is the way I am.
I was speaking to my dealer about something else today. When I mentioned how much fuel I put in the tank, he offered to check my vin number on their system and let me know what he finds.