Multiple Pregnancies from One Mating??

Hello all!! I work in an animals shelter that takes in unwanted bunnies, spays & neuters them, then puts them up for adoption. Today a new volunteer stated that a female doe can have multiple pregnancies from ONE MATING.

According to him he purchased a bunny from the pet store & she turned out to be pregnant. He then said she became pregnant again immediately after birthing and had more babies a few months down the road. He has no other rabbits therefore this female did not have the chance to mate after the initial pregnancy...Is this true? Thanks for any help in advance!