Yes. Please ask your question - even if you're not sure where it fits. We have users that will flag, vote, comment and close it if it isn't detailed enough or in the wrong place.
That being said, it's best to do a little research of both sites to avoid too much confusion if you asked a too user-centric question on Stack Overflow or ask a too much developer-centric question here.
The example is an easy one to answer: This is end user functionality (what is the meaning of the number displayed behind each application) so this fits perfectly into AskDifferent.
If the question is rather "why does the number keep growing in my self-developed app", StackOverflow is definitively the better (and right) place because sooner or later it turns into coding and debugging. But they probably want to see a bit more analysis done upfront than just a "help, my app is eating memory".
In extension to the topics already covered in the FAQ, I currently use the following rules of thumb: If Objective C (or any other programming language besides shell scripting or AppleScript) code or debugging is involved, it belongs to stackoverflow.com. Everything else is usually fine on AD as well.