Ann: Gas Sales Agreement to Deliver Power to Eureka Gold Mine, page-250

As posted above its based on R factor and the % is of PROFIT after ALL costs including exploration/development costs.

As the field becomes more profitable then the % to gov increases.
At the start it will probably be below 15%.

Please do your self a favour and before you post again use the link and go and read how this stuff works from actual contracts. I suggest you search Mozambique from the list / hydrocarbons.
The top one is where I posted the R ratio from.

It does everyone here a disservice banging on about a point when the entire basis for you argument is completely wrong.
https://www.resourcecontracts.org/
Click on the box that say text top left and it will open the PSA in the window. Section 9 deals with profit sharing.