How does the Inverse3 measures its orientation and pose from the handle?

The position is the tip of the handle in the world reference frame.

The Inverse3 end effector query returns a coordinate that represents the precise location of the handle's tip. This coordinate consists of numerical values that define the position in three-dimensional space.

The origin of the position is located at the base of the inverse3, and the coordinate represent the position at the tip of the handle (centre of the ball).