Typing Ctrl+Z twice vs just once

Question

I'm using Windows and CodeBlocks IDE by the way.

If my code was( has space before the %d specifier):

    #include <stdio.h>

int main(void)
{
    int num;
    printf("Enter a number you want to check is present: ");

       while(scanf(" %d",&num)==EOF) // As long as wrong input is present on buffer
       {
          printf("Please enter valid input...\n");
          //clear the input buffer
       }
    return 0;
}

I've have to type in Ctrl+Z twice(once on each line,doesn't have to be at the beginning of line) for the while(scanf(" %d",&num)==EOF) case to run.

Whereas if my code was: If my code was(no space before the %d specifier):

    #include <stdio.h>

int main(void)
{
    int num;
    printf("Enter a number you want to check is present: ");

       while(scanf("%d",&num)==EOF) // As long as wrong input is present on buffer
       {
          printf("Please enter valid input...\n");
          //clear the input buffer
       }
    return 0;
}

I've have to type in Ctrl+Z once for the while(scanf("%d",&num)==EOF) case to run.

So there are 2 parts in this question:

1)Why do I need to press Ctrl+Z twice for the first example? I tried to refer to https://stackoverflow.com/a/21261742/10701114 but it was for UNIX and kind of confusing for me

2) Why does the space before the %d specifier even cause such a discrepancy since it shouldn't matter unless its a %n,%c or %[...] (I got this from https://stackoverflow.com/a/36504282/10701114)?

NOTE: If I should post these 2 parts as 2 questions, please do comment.

Update : I tried this on the cmd prompt with gcc(my first time on a cmd prompt), the same issue persists