Specific procedure for adjusting the consumption indicator with VCDS

Hello, my Phaeton fantasizes in the on-board computer dream consumption – not only in winter (no consideration of heaters and heaters), but also now in summer. Regularly the consumption would have to be indicated between 12% and 15% higher, and that bothers me – I want to have at least half-accuracy as with all my previous cars here. Example last refuelling: 533 miles driven with 53.7 liters (same pump as with the previous beta) This is why I would like to have the ad adjusted up by 15%. Of course, I had already looked at the forum here, and there are some people who were just like me – and it always says in the posts: “Yes, that’s possible by VCDS.” My problem is that the workshop somehow couldn’t do that – it said that I could not do that. Not yet. Since I can’t imagine that some people can do it and some people can’t do it, here’s my question to those who know it:What has to be done specifically with VCDS settings to adjust consumption? Would be very grateful for your hints!