The two guides are to provide different options depending on your own needs.
When we started promoting the 6 Minutes to Skinny program we only had the 7-day fast start guide to get people started quickly with the program and understand the format.
Customers asked for more weekly plans, so our team put together the 8-week guide for a comprehensive guide to the program for customers who like more guidance and don't want to have to remember which workouts they have already done.
The key is to rotate through the different workouts over the course of the weeks you are doing the program, don't just do one because you find it easier or like it better. If you follow the 8 week guide you will definitely be rotating through them all.