Okay, I have found some places that state 20 drops per mL, so it's depending on other factors (temperature, viscosity, purity levels, for example.)
Regardless, the precise input amount isn't crucial. The better plan is to aim at getting ammonia up to something like 3-5 ppm. This will lead to definitive nitrite and nitrate readings. (The problem with trying to define an exact input is that sumps, decorations and inaccurate tank volumes can make the actual volume of water rather hard to determine.)
By the time the tank is fully cycled, nitrate readings will likely be quite high, and at that time, a large WC would be appropriate.