There is some uncertainty on my part of whether you want the value of a pie slice always being displayed or only on hover. On hover is called a
tooltip and the value always being displayed is called a
valueBox in our library.
text:'%t Is A token Value'
Based on what theme you chose, light is the default, the valueBox will be styled and placed in a different position. You can check out the placement attribute for valueBox to see where you can put it here.
When determining what value or
text to display you can check out our tokens.
Simple demo here highlighting tooltip vs valueBox