What does dynamic/run-time customization means?
The customization of the component is either skin or color based and you can dynamically alter the look of the components at runtime using these properties to get one or more component instances having a different look. If you are using the skin properties you need to have the scroller assets symbols in the library exported for ActionScript. You can find what skin and color properties are supported in the Help Book / Customizing the FlashtuningScrollBar component section.