สงสัยเรื่อง C# task ครับ ทำไม ค่า มันออกมาแปลกๆ

 public  partial class frmTask_3 : Form
    {
        public frmTask_3()
        {
            InitializeComponent();
        }

        private async  void frmTask_3_Load(object sender, EventArgs e)
        {
            Task[] writeFileTasks = new Task[20];
          await  Task.Run(() =>
            {
                int i = 0;
                const int sleepBetweenLeech = 100;

               
                for (; i < writeFileTasks.Length; ++i)
                {
                    Thread.Sleep(sleepBetweenLeech);

                    var iCaptureByValue = i;
                    writeFileTasks[i] = Task.Run(() =>
                    {
                        richTextBox1.WriteLine(  "Task " + iCaptureByValue + ":" +  TestRunTask(iCaptureByValue).Result + "  Finish" );
                    });

                }
           
            });

            await Task.WhenAll(writeFileTasks);
            richTextBox1.WriteLine("Task All Finish");

        }
                async void AsyncLeech()
                {

                    const int sleepBetweenLeech = 100;

                    Task[] writeFileTasks = new Task[20];
                    int taskCount = 0;
                    var taskCountOuterCapture = taskCount++;
                    for (int i = 0; i < writeFileTasks.Length; i++)
                    {
                        Thread.Sleep(sleepBetweenLeech);
                        try
                        {
                            writeFileTasks[i] = Task.Run(() => { richTextBox1.WriteLine("Task " + i + ":" + TestRunTask(i).Result + "  Finish"); });
                        }
                        finally { }

                    }
                    await Task.WhenAll(writeFileTasks);
                    richTextBox1.WriteLine("Task All Finish");
                }

                async Task<int> TestRunTask(int input)
                {

                    int sl = new Random().Next(20, 500);
                    return await Task.Run(() =>
                      {
                          int count = 0;

                          for (int i = 0; i < new Random().Next(5, 500); i++)
                          {
                              System.Threading.Thread.Sleep(sl);
                              count++;
                          }

                          //  richTextBox1.WriteLine(" MethodRandom " + input + ":Finish");
                          return count;
                      });


                }

            }