Ann: Financial Report for the Year Ended 30 June 2023, page-38

It is messy, but no trickery. My understanding is that......

The government clips the ticket on every barrel sold, they take a percentage of total revenue, in essence reducing the revenue received for each and every barrel produced.

This can be viewed as the government share being a percentage of barrels produced.
This isn't technically correct, but it does give the same result, and it may be easier to think in these terms.

In addition, BYE have to fork out for all of the costs for each and every one of the (gross) b0arrels produced, including what could notionally be called government barrels.

As I'm sure that you are aware, the hedges are completely separate, and will result in derivate gain, loss or on rare occasions, break-even. These are reported separately.