You got the right one! The amount of drops will depend on the concentration of pure ammonia in the ammonia solution. For 10 gal, add 5 drops, wait for a couple of minutes, measure. If you hit 4, 5 or 6
PPM you are in target. If you read 1 or 2ppm, then add 5 more and measure again; if 3ppm add 3 drops and measure. Avoid erring on the upper side.
Different commercially available brands might have dissimilar levels of concentration. No problems whatsoever.
If your bottle of ammonia is not tightly closed, it may lose strength but you should not worry too much since you will be measuring daily. If you see unexpected variations, adjust as needed, just update your X value and move on.
With the brand new bottle of ammonia solution I needed 7 drops to reach 5ppm in my first tank (10gal); when I cycled my third tank a bit over a month later, a 29gal bow, I was expecting something like 21 drops... right? well... I needed 60 drops.
My bottle is still around, there's some ammonia solution left -have cycled 5 tanks with 750ml of ammonia solution: 10, 5.5, 29, 145, 40gal- but it's a cheap generic one with a low quality cap on it I picked up at the household cleaning section of the supermarket, cost me less than 0.50USD.
Keep us posted and upload pics! way to go bella!
Pepe
Santo Domingo