Rotate B is not a physics object. It is a transformation control. It will keep rotating until the stop button is pressed. Please clear the animation track in the timeline before your next simulation to avoid residual animation.
Speed: The speed will determine how fast will the Rotate B rotates. The larger the number, the faster the movement
Start: The start button will start rotating the prop.
Stop: The stop button will stop the prop from rotating.
Release Object: Release an object that has been picked. This object will no longer behave like Rotate B. The picked number will be subtracted by 1.
Picked Number: The number of objected that has been picked by Rotate B.
Axis: The axis of the picked objects that will rotation.
Rotate B is a transformation control. This type of control is marked with a T sign on the control UI. It has Kinematic attribute which gives collision to other dynamic objects, but not being affected by collision from external physics objects (dynamic or kinematics). After your transform operation, it keeps all the keys on the timeline. Press play and you can replay the animated result; press remove animation keys from the right click menu to remove animation so you can have a new transformation clip.