1st it means what it says! There is a countdown and at 0 the engine will close down. 2nd the problem is vv likely the failure of the AdBlue pump and that really ps me off as 1 it is the result of Audi using an inadequate/poorly made pump, and, even worse, installing it inside the AdBlue tank so that it cannot economically be repaired or replaced. You need a new tank and associated electronics. When the new part is fitted, it has to be registered to the system. Some people, esp in US, say the solution is to ditch AdBlue. That's forbidden in UK and will show up as an MoT fault.