The C on EF means that the specific class and its waitlist is "closed". Makes sense for awards in X since they must be booked at least 24 hours before the flight.
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Thais can be the case, however, IME with Qantas, O9 36 hours before a flight tends to indicate plenty of seats - certainly more than 9.... I wouldnt view high values so close to departure as necessarily being indicative of a quiet flight, just that there are some seats and they could be prepared to let them go to any paid fare ...