Ok, here is what I am getting from this and how to figure out what I should do for nutes.

Fill my reservior to a certain point. Put a mark, then the next day come back and see how much water has been taken up by the plants. Now that I know the plant uptake, I mix a solution with only that amount of water. Then I add it to my reservior that is already filled with the water it needs to make the whole system work. So if I mixed it correctly I should have a res that is almost completely depleted of it's PPMs by the end of the week.

Everything else I have read on this forum has lead me to beleive I want to have the entire systems water at the target feeding ppm.