My saddle is a 31, & it is a medium-wide (this was confirmed by Stubben). A 30 would be a medium. If you want more information on your Stubben saddle, you could try sending pictures to email@example.com
He is extremely knowledgeable & responds very quickly!
Also, the term "VSS" would just mean that it is a saddle designed for jumping, it wouldn't be the model name :) I wonder if it might be a Wotan?