When you 'import contacts' into the system, you may sometimes get the message 'x' contacts couldn't be imported as the email address already exists. This basically means a contact already exists within your account with the associated email. they could be in your archived contacts etc.
To ensure the next time you import contacts, they all go through, you just need to tick 'update' in the duplicate processing box, when your going through the import contacts process.
If you have any other questions, please let us know