I'm gonna take a wild shot in the dark here...I thought I've used that test in the past, and I did find an old box but no instructions...
If memory serves me right, (and it may not, so any elese feel free to correct) that's a "one bottle" test...you take 5ml tank water add to larger test tube and then drip in reagent in counting the drops...
Count ALL the drops...first it will turn BLUE..then as you continue to add drops it will change to CLEAR/YELLOW...
The number of drops you use = meq/l and then you mulitply X 2.8 to get dKh...
It's not an extreamly accurate test, but will get you in the ballpark.
(edit: ) I checked it out with the few drops left in the kit, and those instructions came out very close to my "known" levels...