[SOLVED]Explain How it works?

Question

In a challenge of C language I came across a quiz and found this question about guess the output... but I can't understand how the output is 01
If anyone knows please explain

Edit 12 sep 2019:
<code link deleted, adding code in description >
#include <stdio.h>

int main() {
int n=printf("0");
printf("%d",n);
return 0;
}

Answer 1

printf("0"); will print "0" and return the number of characters that were printed (1 character). The return value is stored in n and printed to the screen

Answer 2

Right answer thanks.. if i change to printf("0000"); it gives output 00004
Thanks again Anna