This is a rehab program designed for grade 1 MCL (medial collateral ligament) sprain.
MCL sprains/tears are very common in jiu jitsu. They might happen due to a sideways impact to the knee, you might’ve twisted your leg when grappling or it could be the result of a leglock.
However it happened, there is probably some inflammation around the knee, pain on the inside of your knee and you probably lost some range of motion.
If the tear is grade 1, start with day 1 immediately. If it’s grade 2 or 3, make sure to do this program in a later stage of your rehab process.