Left thumb up (for me), and right index finger up (with thumb down). That gives us "12 dtg". I call it "Tuelve". Different spelling from "Twelve", but same pronunciation. I decided that, pronunciation wise, I would let it be the synonym that it is.
12 dtg = 34 decimal.
The left thumb is worth 32 decimal, and the right index finger is worth 2. Add them both together and you get 34 decimal.