I think there's a lot of misleading info about chlorine concentrations, particularly about sodium hypochlorite--i.e. bleach, or shock. Please correct me if I'm wrong. Clorox bleach is about 8.5% and pool shock is 12.5%, but that's hypochlorite, and chlorine is only 47% of sodium hypochlorite by weight. So when you quote ppm chlorine, is that pure Cl by weight, or hypochlorite equivalents? It obviously makes a very large cost-arithmetic difference when my gallon of shock is really 6% chlorine, not 12.5%.
Dichlor arithmetic (the commonly available sodium salt, dihydrate) is a bit easier since it's a dry solid, and it is 28% chlorine by weight. So 1 lb in 10K gallons (80K pounds of water) should max out at 3.5 ppm chlorine if completely broken down to free chlorine in the water. The bad news is that about 50% of dichlor is of course CYA stabilizer, which is why continual use of dichlor or trichlor can drive up CYA levels much too high.