Why is the difference between behaviors in for loop?

I am confused by getting the different results after executing the same loops after one another. The first loop Increments the different way and second is completely different.

**Results:**
1 , 1
1 , 2
1 , 3
2 , 1
2 , 2
2 , 3
3 , 1
3 , 2
3 , 3

Code:

#include <iostream>
using namespace std;

    int main()
    {
        for(int outerval {1}; outerval <= 3; outerval++)
            for(int innerval {1}; innerval <= 3; innerval++)
                cout << outerval << " , " << innerval << '\n';
        return 0;
    }