TRYTN supports the ability for a shop to set the maximum quantity of an add-on that is available for purchase by a customer. Perhaps you want to limit an add-on to just one per-person, or perhaps you don't allow more than 10. By default, the system will allow a customer to purchase unlimited of an add-on.
To set a maximum allowed purchase navigate to the product type you wish to sell and either create a new or edit an existing product. On the Advanced Settings screen you will see a section for Add-Ons. If you do not see any add-ons to select you may need to create an add on. Once at least one add-on is selected you are able to modify the maximum quantity.
Setting the Maximum Quantity field to be blank will allow a customer to purchase unlimited of the add-on. Setting the Maximum Quantity field to 1 will present the user with a checkbox during the purchase process allowing them to either purchase the add-on or not. Setting the Maximum Quantity field to anything other than 1 or blank allows the customer to purchase 0 to the value you set in this field and will be able to specify the quantity of the add-on they wish to purchase.