The problem is that by default the Console has a LIMIT of the numbers (symbols) it can display - it is 300 rows
That is why you are seeing the numbers from 702 to 1000...
The solution is simple - just add: Console.BufferHeight = 2000; -> before the for loop.
You can also learn more about Console.BufferHeight by selecting it and pressing F1 (Help).
Here is your code which will display all the numbers required:
static void Main()
Console.BufferHeight = 2000;
for (int i = 0; i <= 1000; i++)