Get down, come down, go down, are all acceptable translations of this phrase. Korean is not that specific. Fred and other great contributors do not have the time to look up all the possibilities in English. They need to add these other options when they get a chance. Thanks to Ash-Fred and all the other contributors to the Korean section of duo lingo
"Please come down" should be accepted. "~세요" implies politeness, so there is an implicit "please" in here. We use "~세요" in polite, honorific situations... that important piece of context should be in the English translation. Please flag this to add the alternative answer with "please".