Clear by parentage means the dog him or herself didn't have to have a test for VwD because the combination of their parents couldn't produce VwD. If that makes sense! Minis, who are prone to PRA, can also be clear by parentage meaning they themselves don't have to undergo testing due to their parents scores.
NOTE ABOUT "vWD clear by parentage": This works like the notation under PRCD above -- if both parents have tested genetically clear of vWD, they CAN'T pass it on to their progeny. By breeding only from vWD clear parents, conscientious breeders ensure that pups will not be affected.