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To do it, first click on the widget and then click on the wizard icon:
Once you're on the wizard, you should find the option to set a max and min selection, there you should set up 1 as max selection.
Once you do that the widget will allow to select only one available ticket, other options will not be available.
Here's my sample form: https://form.jotform.com/62364965575974
Hope this helps.