The Mutation Cycle

Is part 3 of the cyle supposed to be carried on for 6 weeks or am I missing something. It says it’s a 12 week program, part 1 and 2 equal 6 weeks. Then we have part 3 and it doesn’t state how long it is. So, I’m assuming that either there is a part 4 I haven’t seen or part 3 lasts 6 weeks.