Of the thousands of entries, when your number comes up, it then steps through all your choices, checking each one in order. If the first choice date is already full, it checks your second choice, and so on. As soon as it finds a date with enough open slots for your request, then that is assigned to you.
Of course, if it finds no day with enough open slots for any of your choices, your entry is rejected, and then it goes on to process the next person's entry.
Entries are processed in a completely random order.
