Just did this yesterday myself, as I had asked the dealer but they left it on Variable

The MK6 uses the UDS protocol so you can't use the service applications in VCDS
You can do it the following way.
Go Into 17- INSTRUMENTS, and then ADAPTATION
Go to the following channel and change it from ESI to SID

I also changed the mileage to 16100km which equates to approx 10000 miles, I think it was set to 9800 miles

And the time to 365 days as it was set to 372

Resetting the service on the MFD now sets it to 10000 miles or 365 days.
