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.
I have checked your form. Why don't you use RADIO BUTTON instead of a checkbox for that reason?
The main character of checkbox is to have multiple choice. However, the main character of the radio button is to have only one choice.
So that, please add radio button instead of a checkbox as the following screenshot below: