I get the same message in my A3, with S Tronic box. If you read the manual that came with your car, there is lots of warnings (lets call them disclaimers) about not applying the foot brake when the car is in drive. I have stop start on mine and it tells me every time I try to move the gearshift in 'drive' that I should have my foot on the brake even though the car is secured on the electronic brake. I think the book refers to the possibility that the car can lurch forward even though the electronic brake is activated. However, I have learnt that when the stop start is activated and the engine stops, I can apply the electronic brake with the car in drive although the user manual tells me not to do so, but to hold the car on the footbrake, (which burns the eyes out of the driver behind you on dark nights.) As you apply your foot to the gas pedal the engine starts and the electronic brake is automatically released.
If this applies to you, try it for yourself. Engine stops, your foot is on the footbrake, apply the electronic brake and wait until you feel a slight decrease in resistance under your foot, the car is now secure on the electronic brake, so you can remove your foot. Leave some tyres and tarmac between you and the car in front, in case the car starts up again (as it sometimes does), so if it does lurch, then you don't prang the back end of the guy in front.