Both offices are open 09:00–11:00 Brisbane time — 2 hours together.
09:00 you → 16:00 Seattle prev day
10:00 you → 17:00 Seattle prev day
09:00→16:00prev day · Seattle is at work
10:00→17:00prev day · Seattle is at work
11:00→18:00prev day · outside Seattle working hours
12:00→19:00prev day · outside Seattle working hours
13:00→20:00prev day · outside Seattle working hours
14:00→21:00prev day · outside Seattle working hours
15:00→22:00prev day · outside Seattle working hours
16:00→23:00prev day · outside Seattle working hours
17:00→00:00outside Seattle working hours
Working hours assumed 09:00–18:00 local. Offsets include daylight saving where it applies, so this shifts through the year.