There are two types of service schedules - Time and Distance (at 10k miles or 1 year) and Flexible, Longlife service regime which would be done at 18,000 miles or 2 years, whichever comes first.
Sounds like you're on the Flexible regime. Either that or the computer is set incorrectly.
This is from VW website
You can choose from two types of service regimes, depending on your driving methods.
Fixed Service (Time and Distance)
We recommend this service if you are likely to drive less than 10,000* miles in a year, and if you tend to drive in the following way:
Mainly city centre driving, short journeys with frequent cold starts
High engine loading activities, e.g. frequent hill climbs, driving with your vehicle fully loaded and towing
Uneconomical driving using high rpms with heavy acceleration and heavy braking.
Flexible Service Regime (LongLife Service)
We recommend this service if you are likely to drive more than 25 miles a day, and if you tend to drive in the following way:
Regular long distance driving
Driving at a constant speed with minimum vehicle and engine loading, and minimal towing
Economical driving
This Flexible regime has been made possible due to the development of new Volkswagen engines with the latest technically advanced longlife oil. These engines use built-in sensors that continually monitor the oil quality, making it possible to enjoy reliable and confident motoring for up to a maximum of 18,000* miles or 24 months (whichever occurs first).