At my Pool Store they claim their Chlorine is 12.5% but tell me to treat it as 10%. It is really hit-or-miss there. Once I could not get my pool adjusted right with it, so I had to reverse engineer using Pool Math and my final results to determine that the chlorine was only about 6% strength at that time. Out of all my trials with Pool Store chlorine, I have never guessed right at its strength. I am not sure if they keep their tank in the sun or what, but you never know what you are going to get.
It makes it very hard to adjust your FC if you are not sure how strong the chlorine is. I prefer to have consistency from Walmart than guessing with the Pool Store. (Note: Your experience may vary from mine...)