Don't try your cheap tricks on me.

We go from 1 to 5, so the math would be 5-1 +1

You go from 0 to 4, the math would be the same, 4-0 +1

Using 5 as your upper bound, then starting from 0 to 4 is the same as me using 6 as my upper bound then going from 1 to 5.