Sum Of Factorials

The first method returns the factorial of an integer (factorial of 3 = 1x2x3). And the second returns the sum of the factorials between 2 integers. This is correct according to my professor. I'm just confused as to why in the 2nd methods it isn't "total = total + Factorial(i);" instead of what I have.

public class LoopProblems
{
public int Factorial (int n){
int total = 1;
for (int i = 1; i <= n ; i++ ) {
total = total * i;
}
return total; 
}
 public int SumOfFactorials (int start, int end) {

[code]....