haha, this is kind of embarrassing , but you know what? you're the very first person to ask, so i'll tell you: ULC was the first Renpy game i ever published and when i was publishing, it gave me "market" as an option. i didn't really understand it but i didn't want to take any chances, so i just selected every option it gave me, including the market file. to this day i still really don't know what that's for. i suggest just downloading whichever one corresponds to your particular computer.