
I don't know how she could be having a second litter as the Kennel club won't register a litter to a bitch that was mated under a year old.
So at 18 months she would have had to come back in season quickly and this would be a back to back litter with no rest between.
Of course the stud dog owner may be unaware that she has already had a litter and be perfectly happy to accept a bitch of 18 months of age.
Blimey the price is nearly half as much again as the pups in my breed from top lines with all the health tests on parents.