We know it very well. First, it sits in a pile from 1-28 days, depending on the current moon phase, weather, and number of hospitalizations from unfortunate Tony's Town Square diners. Then, a very scary group of sith lords, led by the evil darth vader, decide whether or not the contract will restore balance to the force. If so, they advice Ken Potrock to engage the ROFR demon (this is a real thing), who then uses 0.8 seconds of profit from disney t-shirt sales to buy back the contract. Most of the time that doesn't happen, but sometimes it does.
While that may not be exactly true, that's about as much as is known. The truth is there's probably a small committee at DVD that uses a multi-step formula to make the decision. That formula likely varies depending on all sorts of factors, so from the outside it's pretty random. Best to just submit an offer on a contract you like and hope for the best. If it gets bought back, just try again. Nothing is lost other than the deal.