I tried again and indeed not all the columns shown in iTunes are pasted in Numbers. I swear, geovanile, I'm sure that the first time I got all the columns copied.
Anyway, try this alternative: File -> Print. Then choose Print: Song list and Theme: Custom. When you press Print... choose bottom-left PDF -> Save as PDF instead of real printing. You should get a PDF with the playlist.
The problem with this method is that if you want to have many columns, they will be compressed to fit the paper size resulting with cropped text. Of course you can choose a bigger paper size to workaround this issue.
Another alternative (better in my opinion) is: File -> Library -> Export Playlist... and choose Unicode text. Open the saved txt file in Numbers and, Bob's your uncle, you'll get a spreadsheet with all the data.