See the following descriptions. This shows what the window displays if you are scaling or rotating tangents. Tangent Adjustment Parameter indicates the current location of the tangent manipulation point at any time. Moving the slider changes the point of where you are editing along the curve. You can also type a value for the Parameter value to relocate the tangent manipulation point on the curve.
Scale indicates the current scale factor of the tangent at the manipulation point at any time.
Moving the slider control adjusts the tangent scale at the currently selected point on the curve. You can also type a value for the Scale value to scale the tangent at the currently selected point on the curve. Rotation indicate the current rotation factors affecting the tangent angle at the selected curve location. The Rotation sliders let you interactively adjust the tangent rotation of the currently selected point on the curve. You can also type a value for each of the Rotation factors to be used in determining the rotational position on each axis.