The amount will base on your targetted point. For example, if you wanted to keep Alk at 7-8dkh, then I would start with half the recommended portion and continue to test. You have to dose and test to see how much your tank is consuming per day.
Once you noticed that at set dosage, your parameters aren't increasing or decreasing, then you know that's how much you need to dose daily. Sounds complicated, but it's actually fairly simple.
Focus on Alk first. Get your Mag. up to 1300ppm as you go. Once you dailed in Alk, Ca will just be there. You would dose the same amount of Ca. solution as Alk.
I test Alk weekly now. Mag. hardly deplicted unless you do lots of water changes with low Mag. in the salt mix. The main thing is Alk and more alk. Ca. will fall in once you have your Alk set.
Main thing is, go slow. Really slow and careful to not over dose your tank. Even if you do slightly, it's OK. The system will sort itself out if you just leave it alone for a few days.
Good luck!
