Eric:
What kind of pool do you have?

If you have a concrete/gunite/plaster pool the calcium level should be between 200 and 400ppm.

If you have a vinyl pool, without a heater or SWG, (like most above-grounds) calcium can be anything from 0 to 500ppm--you never need to add it.

If you have a heater or SWG, you should follow the manufacturer's guidance to maintain your warranty.