From looking at a picture of it (as I don't have it), I would believe you'd read it at the fluid line. So when you move the black dot up and down, wherever that fluid line is on the scale when the dot disappears would be your CYA level. I'd think this would allow you to save some reagent if you know your CYA levels are higher (vs filling the entire tube).
EDIT... and when I say save some reagent, I'm just referring to saving some with the 4088 as it requires significantly more reagent than the other taylor test (with just the black dot at the bottom where you need to add liquid until it disappears). I believe the 4088 requires 20ml of reagent vs 7ml with the other test.
Never mind.. I see this was answered in a duplicate thread.
Topics merged. JasonLion