Please help me understand.Im not sure when this forum says keep chlorine at the level of 15 shock level.Question how do you know when it is at the shock level.when I take my daily chlorine this only goes to 5 and the BR Side 10

I am running out of the DPD POWER that I test for cc,I use the bleach cal and have put chlorine in as stated.but water is still a little cloudy.I just need to know when to tell if im at the shock level.
Also where can you get DPD POWER

THANKS