Hagen Nitrate test question

[har-2109]

why does the hagen nitrate test say to use 5 drops of bottle 1&2, but bottle 1 is 10ml and bottle 2 is 17ml??
Surely the extra 7ml will just be wasted.

 

[har-2109]

actually, just had a thought. Bottle 2 is probably a thinner liquid, and so the drops are bigger. Really thought I was on to something then...