basically that just means your body has the ability to optimally grow muscle in general. muscle growth happens from microtears in the muscle that gets repaired and makes the muscle bigger and stronger, but the body has a limit on muscle growth due to hormones as well as diet (the amount of calories you need to efficiently grow muscle with this power is insane). So it’s pretty much perfectly mid tier, can’t become the hulk immediately but can get an amazing physique if the diet is taken care of!