Yes, it is an "extra" ATPL type exam for German Licenceholders...similar to the Flight Planning exam of the JAA ATPLs with some other bits and pieces.
If as a non-German you already have a JAR Licence with the Flight Planning exam credited then I understand the german "Long Range" exam is not required...perhaps they only will need proof of your ATPL passes including Flight Planning.
Doubtless a German colleague will be along soon to give more detail.