Ah now I understand the wording - thanks! (I knew what you said was correct because I've done it, I just couldn't match it to the wording). I had understood it to mean you could not depart from any port within with country, rather than depart the country itself.
I think your lack of confusion is one of those "once you see something you can't see how others don't see it" situations (eg I am not going to read it incorrectly again, now that I know!) So I'm grateful for you pulling it apart so the comprehension hit! 
