Andy,
That text is shown if the user is logged into Joomla but has never logged in and connected their Joomla account to their Facebook account. It's just an easy way to let users connect their Joomla and Facebook accounts so that they can login with either in the future.
If you don't want that text, you can disable the "Allow Reconnections" setting in the SCLogin module. Users can still connect their accounts if you have the "Automatically map users by email" setting enabled or if you are using Full Registration, there will be a login form that user's can login to their existing Joomla account with.
Hope that helps!
Alex