Help me in solving CLB090 problem

My issue

if we don’t write 6 in the brackets after arr then the answer comes as 5 instead of 6…why?
If we are initialising the array along with its declaration, then there is no need to write the array size in brackets like int arr = {10,20,30,40,50,60}; this won’t give a syntax error.

My code

#include <stdio.h>

int main(void) {
    int arr[6]={10,20.30,40,50,60};
	// your code goes here
	return 0;

Learning course: Learn C
Problem Link: CodeChef: Practical coding for everyone

put , after 20 …instead of .