How can change the ID that is assigned to respondents?

I want those completing the form to get a unique ID number in their autoresponder email, and I want to say on the email that they should write the ID number on their check when they mail payment. But the assigned number is really long and cumbersome. Can I change that?

(We're using the form for vendors to register for a festival, but to control costs, we're going to have them mail paper checks.)

If you want to add customize unique ID to your form, please refer to this guide: 

How-to-Add-Custom-Unique-IDs-to-your-Form-Submissions

Let us know if you are referring to something else.