You can edit how the value is displayed by giving it a format like this, where I give it and ending of "Hours" instead of ".0%"

    donut: {
    label: {
      format: function(value, ratio, id) {      return value +"Hours";       }
    }
  },

For more info on this, you can see how billboard does it here. https://naver.github.io/billboard.js/demo/#DonutChartOptions.MultilineLabel