The maximum or minimum number of tickets per booking can be set during the offer creation process. To edit this, navigate in your user account to Manage Offers > My Offers and click on "Edit" for the offer in question.
A detailed description of how to create an offer can be found here.
Under Step 3, "Tickets", click on "Edit" and then on "Options". On “Tickets per order", you can set your desired maximum and minimum amounts.
If you want your Frontend to display more than 20 tickets, it is absolutely necessary to add your desired max number of tickets as shown above. If you do not insert anything, your customers won't be able to purchase more than 20 tickets in your shop.
What the customer sees
If, for example, you have set a maximum of 10 tickets, the customer will be offered a quantity of up to 10 tickets in the drop-down menu in the front end.
The period of time during which the tickets are available for sale can be entered here.