Help me in solving CLB089 problem

My issue

char [4][10] means the array contains 4 elements, but what is the use of the [10] ??

My code

#include <stdio.h>

int main(void) {
    char days[4][10] = {"Monday", "Tuesday", "Wednesday", "Thursday"};
    printf("%s\n%s", days[2], days[3]);
	// your code goes here
	return 0;

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

it’s used to define two dimensional array there.
think of it like calendrer where row consist of days (7) which form column of weeks

I don’t get you