I really do not understand what your trying to say you have a problem with. You are confirming if i am following how things work.
An ad will renew say today for another 5 days if it has not been sold. That is the correct action there is no issue there. Therefore yes an ad will be on your system for 10 days from the very first day it was placed. I mean theoretically if no one buys it it could sit on your site for a year.