Most accurate trip computer I've had ever on this car. Usually within 1mpg from actual.
And so is mine (although whether a 4% variance can really be counted as 'accurate', I'm not sure). It's just that without veryifying its accuracy, it's difficult to rule this out as the apparently low mpg the OP complaned about.
My previous VAG car (Skoda Furby vRS) had a wholly innaccurate trip computer, being a good 6-12mpg over-optimistic. The trained chimpanzees at the dealers, and the combined wisdom of Briskoda knew of no other cases of it being that innaccurate.