can any one help me figure out how this recursion done?

public class RecursiveMethodSum {
 
    public static int sum(int n) {
 
        if (n == 1) {
 
            return 1;
        }
        else {
 
            return n + sum(n - 1);
        }
    }
 
    public static void main(String[] args) {
 
        int x = sum(4);
 
        System.out.println(x);
    }
}

output
10



one question is... during the process of the recursion... (4 + (4 -1)) its == 7? ryt?
but where does the number seven goes? i can only see the the process is just adding
the value that has been passed to the parameter... where are the sum(s)?