Parchment Walkthrough and tips for Number 1's tasks (SPOILERS)

Is it 12 hours to complete all the tasks or does it mean that I must have STARTED the last task within 12 hours? Are we sure its only 12? Someone mentioned that their tasks ran pretty long ... I think they mentioned having a six and a four plus the other tasks all in one day. They calculated it would take 14 hours to complete. At the time I thought (and replied) that they were glitched. I thought it would always be three one-hour tasks and one four-hour.

Now I'm seeing people talk about two-hour tasks ...

Again, 12 hours sounds potentially undoable. Just wondering.