Your vet knows more about Parvo in Egypt than the majority of the people on this forum. I would listen to him. The extra finger is called a dew claw. Dew claws are an extra digit on the hind legs, located farther up on the paw than the other claws, kind of like the front feet. Those are not dew claws and should remain.
Different breeds have rear dew claws in their standards, and some have double rear dew claws in their standards. GSDs hind legs should not have a dew claw, and if they do, they should be removed. The reason for this, is that they can snag something down the line and be torn/injured etc. It is up to you really. The breeder should have removed them in the first couple of days before the nervous system was complete, and it could have been done with a minimum of pain and inconvenience.
If you are planning on spaying or neutering your dog, taking off the dew claw at that time might be the best way to go.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC