# Automatic Calculation Mode

In Automatic mode, the system will adjust the probability of winning a prize based on how much inventory remains. In the example below, we have 1000 pens, 100 t-shirts, and 1 water bottle left in stock. Note how the system displays the chance to win beneath the remaining stock of each prize. Prospects have a 9.08% chance of winning a t-shirt.

Now we’ll simulate three users winning t-shirts. See how the probability has changed on all three prizes since the total prizes available have gone down.