Before revision:  When we focus on the probability distribution of cancellation positions at a certain price level, we find that the PDF increases rapidly in the front of the queue, and then fluctuates around a constat value until the end of the queue.
After revision:  When we focus on the probability distribution of cancellation positions at a certain price level, we find that the PDF increases rapidly in the front of the queue, and then fluctuate around a constant value till the end of the queue.