How does 12306 allocate train ticket quotas in China?

According to the official explanation from 12306, priority is given to passengers traveling longer distances (complete journeys). Only after capacity remains will seats be released to short-distance travelers, with quota distribution also informed by big data on historical passenger demand. This is a public welfare initiative. If it were a purely commercial operation, tickets would go to whoever pays the most—which would likely result in short-distance travelers crowding out capacity, making it unnecessary to build railways to many remote cities.

How does 12306 allocate long-distance and short-distance tickets? Here's the official answer!