The other part of the scene that doesn't make sense to me (unless I'm missing something) is when they first start shorting, it's clear that they're being mobbed

The other part of the scene that doesn't make sense to me (unless I'm missing something) is when they first start shorting, it's clear that they're being mobbed by buyers, plus with the people saying "the Mortimers are trying to corner the market! let's get in on it!" it's clear that there are more buyers than sellers, so the price should keep going up. However, once they start shorting, the price starts dropping (starts at 142, then drops to 102). Does this just mean they are shorting between the two of them far more contracts than the market is buying in aggregate? The movie doesn't make this clear.