Auto Copy is a feature which should copy your files from cards to ND2730, without selecting built-in menus.
That's true if you're backing up a card with new files only, but if you want to update a previous back up, parsing doesn't work and all your files are copied: new ones and old ones again.
1) I take 2 photos and put my card into the ND2730
2) Auto Copy copies two files in a folder called 20120912.000
3) I take an additional photo on the same card
4) Auto Copy copies three files in a new folder called 20120912.001: now I've 2 folders with 5 files.