I've been spending my morning coming up with the complete algorithm. It will be based on a number of factors, taking into account the size of the swap, the number of participants, and how many days the trading runs/
You will get a daily allowance of dibs tickets that you can use. They do roll over to the next day if you forget to spend them.
As trading begins, you'll be awarded additional dibs tickets as people claim the offers you're offering. So as people snap up your items, you will be rewarded with extra dibs of your own.
That's how it will work. The details of what the actual numbers is still being worked on.