2, 4, 6 is the ,02, .04, .06, etc...for draft, it's only a close approx. if you don't have a draft gauge. As you move it OUT away from center, as you see it goes to 2 (left side - LIGHTER weight on center), that will react FASTER and LESS draft is needed to open it.
AS you move it to the right, (heavy), it will take more draft to open (ie. .04, .06, etc)Baro damper?