The U.S. Copyright Office allows creators to pre-register their works in certain instances, such as when a particular work or author has a history of infringement prior to commercial distribution.
Cosynd is not a pre-registration service. When you pre-register your works directly with the Copyright Office, you will be given a pre-registration number. If you use Cosynd to submit a full copyright registration application, you can list the pre-registration number you have received from the U.S. Copyright Office in your registration application.