According to the attached picture, it seems that you have multi-line RadLabel and you would like to change the line spacing.
Note, text rendering uses Graphics. By default, Telerik Presentation Framework uses GDI+ to measure and render the text. You can easily switch to GDI instead by setting the UseCompatibleTextRendering property to false for the respective control. More information about text rendering in TPF you can find here: https://docs.telerik.com/devtools/winforms/telerik-presentation-framework/text-rendering