For 10 days or so, I had kept my pool at shock level for more than a week to kill what appeared to be white mold.

It is gone, but in the process, my chlorine level had soared to 27. Long story short, kit I was using was way off. I have Ben's P234 now and it has recorded these levels of chlorine:
4/29: 27
5/1: 18.5
5/3: 12.5

Other #s are fine and have been. CYA is 20.

Question: Today (5/3), I had a cc of .5. Now, to get rid of that, you must shock, correct? Should I shock with such high reading? According to best guess chart, 12.5 would be right at shock level now.

Thanks in advance. Trying to stay ahead of my water.