Not understanding the subtracting part what number does it subtract from?
The number you sent it. If you send it 5, you can see that it is not greater than or equal to 8, so the 8 action is not needed. It is greater than or equal to 4, so the 4 action is needed. Note that, and subtract 4, leaving 1. That value is not greater than or equal to 2, so the 2 action is not needed. The value is greater than or equal to 1, so the 1 action is needed. Note that, and subtract 1.
Now, perform the actions that you noted needed to be done - 4 and 1.