Depends on how you are growing but like most nute plans it wants you to dump out good nutes every week so you use lots of nutes and have to run out and buy more. I rarely change nutes in DWC so things like that I guesstimate how much they need because if I tossed in a full dose of say, Big Bud, every week I'm sure I'd overdose the hell out of my plants.
What is that stuff by the way?