On the liquid chlorine, it is 10% sodium hypochlorite and the other 90% is probably water. Regular bleach is 6% sodium hypo and 94% water.

When you do the CC (combine chlorine) test, ideally you want the result to be 0, but up to 0.5 is ok. When you have readings that are higher than that, it means you are fighting something in the water and thus the need to shock the pool.