WARNING: This page is about a different car, the 2015 Audi A7 Quattro, 2014 Audi A7 Quattro, 2013 Audi A7, and 2012 Audi A7. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Coolant Reservoir Cap
Courtesy of AUDI OF AMERICA, LLC
The coolant level must be at that MAX marking when the engine is cold.
Coolant level may be above MAX marking with engine at operating temperature.