Your numbers and analysis are correct. In this case, the CalHypo is an inexpensive source of chlorine. Using it, however, will increase the amount of calcium in your pool by about 70% of the chlorine amount -- so a rise of 1 ppm in chlorine also raises calcium by 0.7 ppm. So as a short-term source for chlorination, this isn't a bad option. For long-term or for shocking, you would need to watch your calcium levels and if they got too high you would have to do a partial drain and refill to lower it. Of course, you've got quite a lot of leeway before higher calcium becomes a problem -- several hundred ppm, perhaps a CH above 600 ppm though even then you might not see any scaling or cloudiness depending on your pool's other parameters.

Richard