No idea why that specific number, but hypothetically speaking it might be reaching effectively a Short Singularity.

Allow me to lay out what that means:

In order for the shorters to cover their borrowed shares, they need to buy shares from someone else and give it to the borrower. However, they still owe more shares (because they overshorted so much and nobody is selling), so they will (essentially) buy said shares from the people they just returned those shares to, so they can give those people those shares. Basically, they are paying for shares that they are legally obligated to give back, and then have to rebuy those same exact shares back only to give them right back.

This is a massive oversimplification, but essentially there so many short positions that were aiming to bankrupt Gamestop that now that we are at this point, we basically have a singularity. It's downright insane.