At Shenzhen the company computes the fuel bonus on their super top secret whimsical formula. I get one every month but nobody I have asked has the faintest clue how it calculated whether they be a foreign captain, local fo, or local captain or instructor. I'm told they actually take into account for higher/lower take off weights from the flight planned weight. I know I get one every month and it's always different. It's usually anywhere between $300 and $1000.