Ok , i have just had another look at it
LAX-BNE-PER is 9410 kms which is Zone 9 / 56000 points for Y redemption
LAX-SYD-PER is 9532 kms which is Zone 9 / 56000 points for Y redemption
LAX-MEL-PER is 9605 kms which is Zone 10 / 64000 points for Y redemption
Zone 10 kicks in at 9601kms + , hence the higher points redemption via MEL
AFF Supporters can remove this and all advertisements