I believe you can start the challenge on the 6th or 7th and finish 168 hours later. Therefore you have a window of 8 days in which to spend 7 days doing it. I.e start on the 6th finish on the 12th, because you count the 6th as the first day, I could be wrong though. The key is the 168 hours from when you start.
I haven't started yet so I will finish on the last day. Making it a 4 day roguelike i think.