What I've found, when you know the FC is really high, you can actually use half the water, to the 5ml line, and the each drop of R-0871 equals 1ppm of FC. So if you've been shocking, say to 25ppm, using the 5ml line uses half the reagent of the 10ml, and 1/5 the reagent of the 25ml line. At 25ppm, it really doesn't matter if it's actually 24.5 or 25.5ppm.