It depends. What booking class were you in and what was the flight number under which you booked and which programme were you crediting to?
The Brisbane-Singapore-London would seem correct for a discount economy trip if booked on the BA flight number since earning on BA is typically at 25%. BNE-SIN-LHR is approximately 3816 and 6765 miles, so at 25% , the 954 and 1688 would seem correct. ( there are exceptions to this )
The LHR-SIN-SYD would seem correct for the distance
These total points would also seem correct if on a discount economy ticket using QF numbers outbound and BA numbers inbound if crediting to AA as a Platinum or Executive Platinum member
QF discounted economy ( < K class ) earns at 50% plus gets the same again as a status bonus
BA discounted economy earns at 25% with no status bonus
Can you clarify which scheme you are crediting to and what status you hold and what type of ticket it was?
Dave