forgive me but if a bitch has an undershot jaw is it right to breed from them?

this is what the ad says:

mum too the pups is a show winning bitch shown at championship level she has perfect mouth and bite with the slightley undershot jaw

isnt this contradictal?

oh someone tell me what this means please?
sister is after a frenchie and has asked me to help her look for a 'nice healthy' pup.
ill do my best but dont want to dismiss this litter because im not sure of something.

If you read the French Bulldog Breed standard on The Kennel Club site, it says "mouth - slightly undershot." so slightly undershot is coreect for the breed.

According to standard they should be slightly undershot
http://www.thekennelclub.org.uk/item/159

ah haaaaa!!!
ok ill give that a proper read through first then doh!! thanks