A Few Terms
CoS = conditions of service. This is your contract, but be warned that in Hong Kong your contract may be different from others: ie pre-'93 A scalers are on their original contract with modifications, and today's new joiners will be on a completely different set of benefits and salary. The company can unilateraly improve your contract, but any concession must be "negotiated". The Cos 08 negotiations are dead, there is no payrise for current pilots. It is possible that new hires will still be offered the Cos 08 contract.
G Day = guaranteed day off. You can count on having this day off. 10/month.
O Day = operational day. This day belongs to the company, but no duty is scheduled. Usually added to the end/start of other duty, in case they might need you. If they don't, it is a day off.
A day = "on call day". Call the day before, and be on call for that day.
Roster = schedule
Sector = leg
Coaming = glareshield
Pedantic = pays sufficient attention to detail
I hope that helps.