My 2010 MINI (BMW-made) has the same deal, and you could use the stats it gives you (kilometres until empty, average kilometres/litre, and actual tank size in litres) to calculate what's left in your tank, but why not just add it to the displays that already exist?

I also notice European cars (Audi, BMW, MINI, Saab, even VW etc.) tend to be more accurate and linear than American/Japanese vehicles. But that's just me.