The foundations classes are there to ensure that all participants understand the principals of scaling and know how to perform the movements safely. Using the correct technique ensures you get the most out of the program and are not a danger to yourself or other athletes. Some of the movements are complex and require a high-degree of coordination and body control: these movements are best taught in a special series of progressions which allows people to learn the movement patterns more easily. Athletes who have not gone through the learning progressions often develop flawed movements patterns which affects their performance in the longer term.
To fulfil the CM2 Foundations requirement you must attend five Foundations classes. These don't have to be consecutive, you can mix and match to suit your schedule. Five is the minimum number of classes you are required to attend but you can continue to do the Foundations classes for as long as you feel necessary.
These classes are also appropriate for any athletes who may have moved on to the mainstream classes but feel they need more work mastering the basics or developing the technique to move onto the next progression in certain movements.