Did you have a stopover in Dubai?
If not, then it will have been ticketed as QF 2 LHR-SYD as a single segment and same for QF1 SYD-LHR giving a total of 2 QF sectors
If you had a stopover , then you would get 2 sectors
Also if you flew QF10 LHR-DXB and then QF2 DXB-SYD, that would count as 2