Basically what your trying to do is maintain the stability and levels of the foundation elements.
So ideally you add these daily, for example with an auto doser, according to daily usage, and this will keep the levels stable for you. You could also do it manually but it will be a lot harder.
So test you water on day 1, don’t add any foundation elements, then maybe test on day 4 (or whatever you choose) and then see how much of each element has been used up. Then by simple division you have your daily usage to add each day.
Alternatively you could dose once a week by just adjusting the levels weekly, but this is less desirable as over the week levels will drop, and hence the stability is not as good.
So I think in answer to your question, the amounts are either daily or weekly depending on how much your system is using.
I hope this helps?