This mod simply changes some game text to display the actual XP and Payout (Cash) multipliers instead of "Tremendously increased XP and Cash"
For visualization look at the screenshots.

The values are from the game code.

XP gets a "Risk Bonus" added which means in the example of Death Sentence that the base XP value of a contract gets multiplied by 14 and that value will get added to the XP at the end of a heist (look at the screenshots and look at the one that lists all the XP)
So you always get the same base XP for a contract but the multiplier gives you the base XP multiplied by the difficulty value added on top.

Payout (Cash) multiplies the "Job Payout" cash.
With Art Gallery as an example it is 30000 * 13 = 390000
390000 + 30000 = 420000 (effectively making it a 14x multiplier because there are no extra bonuses unlike with XP)