To add a quota to products, navigate to the Product Management page (Settings -> Products).
Hover over the product that you want to add a quota to. Click the Edit button to the right of the product name.
A menu will appear to the right of the page that will allow you to make changes to your product. Scroll to the bottom and click the Quota Settings drop-down.
Item in user’s cart: If you’d like your registrants to take up a spot in your quota right after they have selected this product, enter the quota number in the box.
Note: When using this quota, registrants will not be required to pay anything before taking up a spot.
To require payment in order for the user to count towards a quota, set the quota then turn on the cart timer. Here's how the cart timer works
You’ll also see an option here to Allow Waitlist on specific product types. Checking this box allows registrants to select this product even if the quota has been met, but will add them to a waitlist. You can determine later if you’d like to allow waitlisted users to add this product.
For products that are sessions, locate the specific session you’d like to add a quota to and click “Edit Session”.
Under the “Options” tab, scroll down and click on “Quota Settings”
How to set a cart timer/paid for quota