In order to display the Ticks of the RadSlider you need to set the TickPlacement property of the RadSlider as its default value is None and no Ticks are displayed, for more information you can check this article
. After that you need set the TickFrequency property which is responsible for how often the ticks are drawn, for more information and code snippets you can check this article
Please note that the RadSlider and its Minimum/Maximum/Value/SelectionRange properties work with Double not Decimal values.
I hope this information helps. Please let us know if you need further assistance.