Doughnut Chart displays the relationship of parts to a whole component. First you need to generate a Table Chart then modify the chart to create a Doughnut chart.
For example, QA Manager wants to see test case counts categorized by their execution status. So they want to generate the Test Case by Execution Status chart.
The fields required in the report are: Test Case Execution Status, Test Case Key
Label: Label always holds single test entity fields with any value.
Value: Values always holds single test entity fields with any value.
Once you save the gadget, it will be available in QMetry Custom Gadget > My Gadget tab.