According to $scope.Stat array object you have access each as $scope.Stat[0].Validate

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$scope.pieData = [{
 name: 'CheckLists Socred',
                y:  $scope.Stat[0].Validate,
                color: '#00c853'
            },{
                name: 'CheckLists Not Socred',
                y: $scope.Stat[0].NotValidate,
                color: '#b71c1c'
        }];