Event Participant records assigned to Default Contact should be assigned to an actual Participant.
For more information about how these get created in your system, see Default Contacts.
The Customer Portal Report Card gives an A grade when you have a decrease of at least 5% from previous month (or none). The number counted is Event Participant records associated with Default Contact.
This tool is able to review registrations and assign a Participant. See Assign Participant Tool.
See Portal Login/Authentication