Why TaskFactory.StartNew Task is not starting immediately?

As per the MSDN Documentation TaskFactory.StartNew it Creates and starts a Task. So, for the below code sample

class Program
 {
     public static void Main()
     {
         var t =Task.Factory.StartNew(
                 () => SomeLongRunningCalculation(10, Display)
             );
         var t1 = Task.Factory.StartNew(
                 () => SomeLongRunningCalculation(20, Display)
             );
         Console.WriteLine("Invoked tasks");
         Task.WaitAll(t, t1);
         Console.ReadLine();
     }
 
     public static void Display(int value)
     {
         Console.WriteLine(value);
     }
 
     public static void SomeLongRunningCalculation(int j, Action<int> callBack)
     {
         Console.WriteLine("Invoking calculation for {0}", j);
         System.Threading.Thread.Sleep(1000);
         if (callBack != null)
         {
             callBack(j + 1);
         }
     }
 }      
 

My expected output was

Invoking calculation for 10
 Invoking calculation for 20
 Invoked tasks
 11 
 21
 

But, it is displaying

Invoked tasks
 Invoking calculation for 20
 Invoking calculation for 10
 21
 11
 

I would like to learn

1. Why the tasks are not running immediately after StartNew?


2. What should I do, to get the output in the expected format?

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