JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
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.
We have an inventory widget where you can define the number of stocks/quantity. This will be automatically deducted on every submission.
You can select which of these widgets you want to use.
Unfortunately, since you can't create a condition on these widgets that fetches the number of quantity left, I'm afraid you can't connect it with creating an email notification condition.
However, you can always create and email condition if you want to. To show an email field for the user to fill in their email address and get notified on a separate notification, simply create an email condition.
Example (showing an email field and email condition).
If you need further assistance with this, let us know.