What does "registration complete" mean?

Registration of additional travel information needs to be completed before Check-in completion. You can use Mobile Check-in and Self Service Check-in Machines.
However, in the following cases, you will need to check-in at the airport counter on the day of your flight even if your registration is completed.
・For flights or routes where mobile check-in and self service check-in machines are not available.
・Passengers with certain types of visas
・Passengers requiring assistance
・Passengers who cannot use mobile check-in and self check-in kiosks for any other reason.