in an adult dog the ideal is for the tail to be level with the top of the skull, I could show you if the pups were in front of me as its a little hard explain, not all pups have same length tails either, in my own pups ive had taken off 1/2 - 1/3 but whatever you do dont relie on your vet to get it right as ive seen some right fuckups from vets used to docking pet russels etc