The default tracking behavior is scrolling, where the dial position of the slider is changed gradually. For example, by holding down the select mouse button while the pointer is positioned on the indicator line of the dial, you can move the mouse and cause the dial to rotate. This gradual changing of the dial value might be desirable for a volume control.
If the CSS_POINTSELECT style is specified for the circular slider, the position of the dial is changed immediately to a point on the scale that has been selected by the mouse. Point selection allows value changes to occur immediately.