The sentence is worded almost correctly. It is a little sloppy. However, what it means is clear to a native speaker. It would be clearer if it said she "was paid $990 for lost earnings," or, even better, "was paid $990 as compensation for lost earnings." Let's say that this stuntwoman is normally able to earn $2,000 per week. Suppose that due to an injury, she is out of work for five weeks. She would have earned $10,000. Since she was out of work for five works, she earned $10,000 less than expected. This is like losing $10,000 in earnings. She has lost earnings of $10,000. This stuntwoman has lost far more than five weeks of work. She has lost her arm and probably will not be able to work as a stuntwoman ever again. She's lost her whole career. Maybe she has lost several million dollars in future earnings. The stuntwoman believed that the producers had insurance, and that if anything happened to her, they would pay her back for her lost earnings. However, she was paid only $990. This seems unfair because of "the film's blockbuster success and gross of more than $300 million." The film had gross earnings of $300 million. Of course, the net earnings--after expenses are paid--would be less. However, it does seem as if the producers had plenty of money. It seems as if they could, and should, have paid her much, much more than $990. I found a link to the story: https://www.goodmorningamerica.com/news/story/resident-evil-stunt-woman-felt-abandoned-producers-losing-65632947 It helped me to understand the context.

Lost earnings = money she would have earned, if she had not been injured. As for the "in," it really should be "for." But "in" is often used to show type or category. (Eg, "I earned $100,000.00 this year: $80,000.00 in salary and $20,000.00 in commissions on sales."

Yes, sentence is worded correctly. 'lost earnings' is a term used to describe future income 'lost' because you can no longer work for some reason or you have lost the ability to make as much money. Jackson got injured during her job on the film and now can no longer work to make money, or she is unable to make as much money as she could before. This future income is 'lost' because of injury - she cannot make as much now. Often if someone else is at fault (they caused your injury) you can take legal action and claim an amount of money as 'lost earnings'. This amount is supposed to compensate you for what you will lose because you have lost the ability to earn as much as before.