What it's not telling you is how much Free Chlorine it will add to that 2000 gallons (or whatever). With out it, it's a pure W.A.G. (wild-a..-guess).

You also need to be testing your water so you know how much went in. Testing is THE critical part of pool maintenance.

Cal-Hypo (from HTH) used to be 68% chlorine. Now it's mostly 48% chlorine...that's hard to recommend. If you are going to use it, you need to monitor 4 things:
Chlorine levels (Free, Combined and Total)
Stabilizer levels (CYA, Cyanuric Acid)
Total Alkalinity
And
Calcium levels.

If you have a concrete pool you want calcium to be between 200 -- 400 ppm. Beyond that, do NOT use Cal-Hypo.
If you have a vinyl pool, calcium can range from 0 to 500 ppm, but no more.

If your Total Alk is too high and your calcium is high, you can get milky water.

So I can't tell you how much Cal-Hypo to use. With all that other info, I could hazard a REASONABLE guess and then you could test again and see what you got.