If you are selling something that has a limited quantity, such as seats in an event, then you may opt to use our Events Field feature OR use the following to steps to ensure you are not overselling seats, inventory, etc.
In the Form Builder Tools for the form, drag and drop the Checkbox field to add the checkbox field to the form. Next, set the label to the name of your product, and check the "Unique" checkbox. It is better to leave this field un-required, more about that below.
After that, scroll down to the options section and add all of your "seats," such as Seat 1, Seat 2, Seat 3, etc. If someone selects all of the options on the form, the form will shut down. So if you can get away with the field not being "Required" you will be better off.
Now when you preview the form and choose an option then submit. Then next time you load that form the option will not be available.