Not all spin actually contributes to a pitch’s movement. For a football, or a bullet, none of the spin contributes to movement, and so, a football or a bullet has 100% Inactive Spin. In order for a baseball to have Inactive Spin, you would twist your arm slightly so that the baseball is thrown more like a football. The more the baseball is thrown like a football, the more the spin of a baseball will go from Active Spin to Inactive Spin.

When thrown with pure topspin or backspin, then 100% of the spin contributes to movement. You can also throw a pitch with some side-action so that some of the deflection will go up or down, and some will go side to side. All of this is Active Spin.