The first thing you need to look at is the size of your beard. Depending on it you will know whether you need to use 3, 6, 10 or more drops.
The second factor is the density of the oil!
You need to look at the beard oil you are using. Some oils are light, easy to apply which means that you can use 1-2 additional drops. On the other if you are using a heavier beard oil then limit your usage you the lowest quantity indicated about. You do not want your beard to fill sticky and too shiny.
How about that heavy scent coming from your beard?
Some beard oils are unscented, some have a strong woodsy feel, some are sweet, spicy or even fruity. If the beard oil you are using has a strong scent, consider applying fewer drops.
A few additional notes about the quantity of beard oil to use:
Most beard oils are made of all natural Carrier Oils mixed with Essential Oils. It is important to always make sure to read which carrier oils have been used in the mixture. Some carrier oils such as jojoba oil can create skin irritation if used in the wrong percentage (usually above 10%).