What to do first? CYA > 200 ppm

[PoolLizard]

My "shock" (Di-chlor) from Costco says this on the label:

ACTIVE INGREDIENTS:
Sodium dichloro-s-triazinetrione.... 58.2%
OTHER INGREDIENTS.................41.8%
TOTAL INGREDIENTS.................100.0%

How do I know if it's UNdiluted dichlor?

I now have an 8 oz bottle of R-0013 reagent, so I'm going to keep testing the CYA level about every other day while I'm adding the dichlor. I don't want to overshoot the target and have to refill the pool again. Taking it cautiously while still maintaining the FC at 7 - 10 ppm.

Is this stuff a good price? Even at their sale price, it seems a little pricey to me.
http://tinyurl.com/l5fk6mv