What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
It is definitely doable. Please use "Inventory Widget" in order to make it work. You can create your product on the widget and limit its number to 56. You can then use "Form Calculation" widget to calculate the total price and make it pass to the payment field.
Please see an exemplary video here: http://www.screencast.com/t/wvBMKrTNZKCy
This guide of our should also be helpful: https://www.jotform.com/help/275-How-to-Pass-a-Calculation-to-a-Payment-Field
Please check these and let us know if you encounter any issues.
Thank you for contacting us.