It evaluates the hip scores of the individual dog as well as the other dogs in the pedigree.  100 is considered normal, the lower the score the better.

Vollkommen German Shepherds SV Hip Certification

ZW score is a measure of Breed Worthiness.

SV (German Registry for German Shepherds) ZW (Breed Worthiness) Data Base contains Hip evaluation results for 167 vom Vollkommen bred German Shepherds