The main purpose of the program is to improve your shock and strength in squats and strengthen your whole body.
It is important to remember that you have good control during the RM exercises. Build calmly and methodically towards your RM. When you feel that you are losing control of the technology, it is time to pause.
-10% or -15% means backoff set from your RM weight in the specified exercise. Example: If you kneel 100kg on 3RM, a backoff set with -10% would be 90kg.
It is NOT a program for beginners! You should have a significant amount of strength training in your luggage. Make sure you master Olympic lifting before you start the program or have a trainer who can show you the right technique.