Alk. Dosing help.

[reeflife89]

I've been trying to bring my alkalinity into the acceptable range 3.5 - 4 meq/l. Currently my pre mixed salt water change water is around 2.0 meq/l. Ph is 7 and cal is 490. Trying to wrap my head around the ph alk cal ratios maybe someone has some easier to understand material ? Or any dosing or buffering help would be appreciated.