The seat map does not reflect the actual number of reservations for a particular flight. It is a common mistake trying to predict the loads of a flight from the seat map available. You can easily have fight that is fully booked, however, with many unassigned seats. Many reservations are with no ASR, e.g. group bookings and for carriers where ASR is for a fee. It is almost certain that your flight will have many more pax than 5 or 15 at the end of the day.

Most likely your flights will depart pretty full - airlines are very good at this mind you.