How much soy lecithin to use?

Hello everyone, I'm sorry if this may get more technical then usual. I want to use soy lecithin to emulgate 2ml of infused cannola oil into 500ml of refrigerated milk. The usual recommendations go from 0.5..2% of liquid/mass in lecithin. So far so good, but I am curious if it is possible to calculate an exact amount needed. If I understand correctly, lecithin works because it's molecule is attracted to both fat and water and forms a sort of "shell" around the fat. So the amount of lecithin needed should be solely dependend on amount of oil want to emulgate, because once all oil is "shelled", any excess lecithin would not have any benefit. How can that be calculated? What am I missing? Thank you for your input! submitted by /u/patteb