donut chart value AND wallpaper dimensions

You can not add a value in middle of the donut chart. Still, You can add by creating a new card or text box for custom value. For example you want to show employees and profit in donut chart by default no method to show value in middle, So Don't worry add new card put profit as the value in card then select donut chart go to format setting select background, and choose 100% transparent then drag your donut chart above Card you created. Whenever you will select slicer value it will reflect accordingly,