Even though the reservation has been completed, the remaining seats will still be marked with 9. Why is that?

Reservations for air tickets are divided into individual and group reservations (at least 10 seats).
The maximum number of seats shown by the system will be marked up to 9 even if there are more than 10 seats left available, as only individual reservations can be confirmed over the Internet.
Actual residuals 8,7,6,5 are shown only if available seats are less than 9 seats.