Yes, the weight change was in take-off weight, not the change in fuel.
The plan, which allegedly was given late to the flight crew, advised that the plane was carrying zero passengers and, as such, required less fuel than it actually needed to get to Perth. “This meant that all the supplied flight plan calculations were based on a flight 14,660kgs lighter than the actual aircraft weight,” the April 1 report found.
I don't know what the figures are for the 320, but the 737NG often works out at around 10% & I imagine the 320 would be similar. Therefore, a 14,000 kg increase in weight would give an increased burn of about 1,400kg. Plus the extra for VR, FR, etc.
However, SYD-PER is most likely an EDTO flight & if so, perhaps the most important issue regarding fuel is the EDTO requirements. Most, if not all, operators would
require a new plan for EDTO operations with a weight change of the reported magnitude. Perhaps that was the reason for both crew members being initially stood down.