I think its for bigger teams: "Have a team? Great! Everyone on your team gets their own 3 hours! One person may focus on one part, another on another, and so on. There are no restrictions on team sizes, so invite your friends!"
Yeah, three hours is a self-imposed time limit. To fit people’s schedules, they give you three days in which you can pick when you want to code aslong as that is only for 3 hours. This helps people with work/school or people in different time zones for who it is night/early morning.
