One offer per place
A freed place is offered to the front of the queue, by link.
In the paid plans
A cancellation frees exactly one place, so exactly one person is offered it: the one at the front of the queue, by a link of their own.
Nobody else can take it while the offer stands, so the place is not sold twice and the queue does not turn into a race.
More in Waiting list
A full night is not a dead end: the queue turns a cancellation back into a sale.