After algae clear, when do I stop shock

[TRHOD12]

Would the shock also make my CYA level read high??
I had the CYA level checked at the local pool 2 weeks ago, and checked it with the 234 kit earlier this week and the level was 30.

edit--Today when I looked at it, it appeared to be 50.

I guess the take home message when shocking is not to look at the other chemistry?? Would that be a safe assumption??

Blessings,