Wondering how to work out dosages on medicated creams (Non Anabolic)

[ruffcute]

I needed to work out the dosage on a cream. But not usually working with creams or anything like this Im having difficulty trying to figure it out.

The cream is medicated and has 80g in the bottle and is at a concentration of 2.5% of whatever the chemical it is (Im at work and cant recall the actual name)
apparently I need to use 0.2 mg per kg of body weight. Im 100 kg so I need 20 mg of cream per application.

Am I missing something here. How would I work that out?

Any help please.