Dublicate files?

Hi!

I was wondering how RB works. 

Say that if a have two playlists with the same song. I've exported them on different occasions. Will the RB transfer a new .mp3 to the USB or will it point to the existing .mp3 file on the USB that is already there? So the both playlist will point to the same file. 

The problem is that i dont want to have dublicate mp3 files to take up space on the USB. I hope they programmed it this way. It makes more sense, but im not sure.

Hope you understood, if not, reply and ill try to be more clear. 

/Joey