"How long is a piece of string"?
It depends on the journey, your driving style, and the size of your fuel tank (34L vs. 42L). I get 71-75mpg out of my TDI, other drivers who have to cope with short trips in city traffic only get 50mpg. I don't have a FSI so I can't answer that specifically.
I would guess that in ideal circumstances (brimmed & vented 42L tank, long journeys with careful A-road driving @ 60mph max) it might be 460, for the small tank, short city journeys & spirited driving, it might be half of that. But these are just rough guesses.