WARNING: This page is about a different car, the 2018 Audi A6 Quattro, 2017 Audi A6 Quattro, and 2016 Audi A6 Quattro. However, it is still accessible from the selected car via links, so may be relevant.
The Bolt -2- Attaches The Starter To The Transmission And Also Has A Spacer -Arrow-.
Courtesy of AUDI OF AMERICA, LLC
The spacer sleeve must be inserted between the starter and the transmission.