I bought a vial of "100" once. Well, it was 100
drops, but those were strong drops. Really, really strong.
Ho, boy.
I made a ritual of dosing it too: only I distributed the liquid, and nobody got the liquid unless they "assumed the position", which meant they were on their knees, hands cupped upwards in a begging manner, tongue out, and staring me right in the eyes. All went well until I trusted someone else to dose me, and they gave me 3 instead of 2.
That night was a wild ride, lol.
But yeah, if it's in a vial, just squeeze gently until a drop forms and falls from the end. Drop size depends on gravity and surface tension, so on Earth and at one atmosphere (ie. approximately everywhere) it's fairly constant.
Share and enjoy