special english 中 this is America 里的一句口语,请问为什么there's only t

special english 中 this is America 里的一句口语,请问为什么there's only two things...不用there're?
"The only thing that we always try to stress is that a stay-at-home dad can do the same things that a stay-at-home mom can do.I always like to joke with some of the new dads that come into the group that there's really only two things that a stay-at-home-dad can't do,and that's give birth and breastfeed."