A Coradine Account is an in-app account system that allows you to use your LogTen subscription on multiple devices. The Coradine Account is separate from and does not need to be the same email address as your AppleID /iCloud account. You can have one email as your Apple ID and a different email for your Coradine account.
The Coradine account system does not keep your logbook data. It is only used to verify subscription status. All logbook data is stored locally on your devices or in a Backup you create via iCloud or Dropbox. To back up your data please see our In-App Backup article.