Can you post here what you got for RODI systems? At one point I think you said you ordered 2 stage systems but the smallest I've seen is a 4 stage. (Granted, I have definitely not looked at every RODI system in the world
I think it'll help people here help you if you use the terms typically used in reefing forums.
Tap water is untreated water that you would drink. Whatever comes out of the tap at your house/business
RODI water is water that has specifically been filtered to remove all the "stuff" in tap water
Filtered water: Water that has been filtered to some degree but is not RODI water
RODI water doesn't have all the things corals need. RODI water is a blank slate so you can add all the things corals need and know exactly what's in your tank.
The salt you have will contain calcium, alkalinity, magnesium, minor and trace elements.
Corals consume alkalinity and calcium especially quickly.
You can replace those elements either by doing regular water changes or by dosing. Either way you should be testing regularly (at least once a week but really probably every day if you're trying to figure out a dosing schedule).
When you dose you only want to replace what has been consumed. As another poster said, you want stability.
I'd be worried that the Kent Marine product is going to eventually make things in your tank unbalanced. It's specifically for growing coralline algae. There are much more precise accurate ways of dosing (and probably it's cheaper to dose two part manually as well). Do you have an ATO on the tank at your father's business?