PLEASE HELP ME

Ok I saved all my 500 + contacts. Good thing, because my iPhone recently crashed and I had to RESTORE. I had not BACKED UP my phone since March 2011. Phone up and running now. BUT I have my contacts from my SIM card on here and all that had been backed up BEFORE march 11. So MY QUESTION: when I send my contacts BACK TO MY PHONE FROM THIS APP, WILL IT CAUSE ME TO HAVE DUPLICATES ????

Honeybeemiles about iBackupContacts, v1.4