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.
You can achieve this when using the Inventory Widget.
Here is a demo form https://form.jotform.com/61471146729964
As you can see in the demo form, every time an item/products was used, the inventory count diminished.
You can setup your Registration form with the same concept.
Set a limit to the number of registration available. Once all registration used up, the user will not be able to register or used the specific item.