Factual error: When Beeks is locked in the cage with the gorilla, it reacts in an overtly aggressive and sexual manner. First, gorillas are shy and gentle creatures. The male gorilla would be scared of him, not the other way around. Second, gorillas identify each other by their smell, and the smell of a female in heat is very specific. Beeks would smell like a horsehair rug and the male gorilla wouldn't be the slightest bit interested.
Factual error: The Amtrak Metroliner has open passenger coaches, not the European-style compartments as seen in the movie. (01:30:45)
Factual error: The stock exchange shouldn't be open on New Year's Day.
Answer: Without knowing precisely how many stocks Winthorp and Valentine sold at the beginning, there is no way to get an exact figure. But we can make some educated guesses. Frozen Concentrated Orange Juice is sold in contracts, with each contract containing 15,000 pounds. By the end of the day, Winthorp and Valentine were making at least an 84 cent profit on each pound, and $12,600 on each contract. If they sold 20,000 contracts, their profit would be $252 million. Considering the Duke's lost $394 million, that estimate seems to fit (and is likely even a little low).