WARNING: This page is about a different car, the 2017 Volkswagen GTI, 2016 Volkswagen GTI, 2015 Volkswagen Golf, and 2015 Volkswagen GTI. However, it is still accessible from the selected car via links, so may be relevant.
Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
A plastic overflow tube is located behind this screw -arrow- (with 8 mm hex socket head). Its length determines the fluid level in the transmission.