What is the difference between contacts and seats?
A ‘Seat’ is a user whom you have added via settings and has full rights (to upload content, etc within your account. They will also appear as a contact.
A ‘Contact’ is someone who you have added as a contact (to share content with) or who was synced when you imported or connected a list.
Contacts have no rights within your organisation except for any content viewing rights you have assigned to them.