Chicks absorb the yolks before they hatch. They can go 72 hours or longer just on that yolk, without other food and water. That's why they can be shipped in the mail. Just because they can go that long doesn't mean they need to, but 48 hours in an incubator is no stress for them at all.
Thanks for the help. I was also concerned One of the 2 chicks was weak and could get out of shell after 5 hrs I help him get out and he barley was moving, but today hes doing much better in the incubator. Thanks again