How to add sequential numbers in form?

Finally, please could you tell me how to add sequential numbers please? I'd like to start at number 401, and then add 1 for every successful application. Thank you.

Yes it is possible to achieve your requirement by adding "Unique ID" widget whcih will allow to add sequential  number in form and set the prefix and padding numbers in form.

You may like to take a look at the following guide which should help you:   https://www.jotform.com/help/79-How-to-Add-Custom-Unique-IDs-to-your-Form-Submissions 

Hope this helps.

Do try it out and get back to us if you have questions.

Thanks Ashwin :)