if you have 13 cookies, and I ask for 4 cookies, how many cookies do you have left
I'm pretty sure I'd still have 13 cookies.
Let be clear this question up a bit by adding my own characters.
Angela has 13 cookies, and Peter asks for 4 cookies, how many cookies does Angela have left?
Now this answer depends on what happens next.
Scenario #1: Angela is selfish and keeps all the cookies for herself.
If Angela keeps all the cookies then Angela will still have 13 cookies and Peter will have 0 cookies :-(
Scenario #2: Anglea is kind and shares the 4 cookies with Peter.
If Anglea shares 4 cookies with Peter then Angela will have 9 cookies and Peter will have 4 cookies.
Hope that helps!