The rating and there are two different systems just tell you the dogs condition in terms of a grade. Why is this meaningful? Because it is one factor of many that may be linked to hip and elbo issues. If it were the only issue the problem would have been greatly reduced through breeding. There is now a thought that weight, expose to jumping early on, and Neutering before the dog matures all play a part. So, look for good hips for at least a few generations. Warrenties may make you feel better but think about the warrenty. Unless the wording states you keep the dog and get a refund or something along those lines, you still going to have to make some tough choices. Get good rated hips, keep the dog lean, and don't nueter too early. You vet should be able to find literature on what is now the thought around too early for large breeds. If he can't find a new vet. Keep in mind these dogs are work. I have had dogs my whole life and grew up around dogs. A working Shepherd is designed to want to work and if not exercised they will act up. I have had mine 2 months and he has put some miles on me for walks. You can't run them much until the bone plates are done growing so toys, tug, walks long walks are the key. I don't regret getting mine, but the whole Schutzhund thing has turned out to be more of a good sounding idea than reality. You can find multiple threads on here about difficutly find a group you get along with and that knows what hey are doing. I have done a lot with mine in two months using my knowledge from traingin the last two non GSD's upsdie is the GSD learns in nothing flat, down side is there are some behaviors like dealing and using food and prey drives. You can use drives to train but sometimes the drive goes the wrong way and they start looking at bikes, cars, running kids. So now you trying to train appropriate times to engage in prey etc.. I know your pain. Hope this helps.
Olaf von Falkenhein