Yeah, that is an odd number. But you could see that on your power feed into your home.And where are you going to get 277 volts? That is an odd number.
Power companies will have to turn up the voltage to push enough power to cover the power loss that is created by wire length. So if you're closer to that transformer, you could possibly get 277v and if you're at the end you could be getting 220. I've seen 218v in some homes that are farther out in rural area's.