Im a little confused, what do you mean by in line with what is going in?
Lets say my mixture is 1000 ppm going in, 800 runoff. Guidlines say to have a ppm of 1000. Do i need to get the runoff number up to 1000 by feeding a little more?
Feed the 1000 until run off exceeds the 1000. Balance. You want them as close as you can get. If you feed twice and it jumps to 1200 in run off, you should do water only (if soil) or decrease your input by a few hundred points. Until it drops back in line with your average feed.