How to set min and max value of number field?

I would like a text field, "Unique Order ID # (that we made a numeric value) force the user to have no less than five digits. If they enter four, we'd like them to get a message. This field is also our unique question in preference because we will mail an invitation to all our customers that has a Unique Order ID # they must enter on this form. And we don't want them to be able to submit it multiple times. We tried the Quick Tools/Number option, but that doesn't work in the "unique question" section in preferences. So I was wondering if the conditional logic might help get us where we need to go on both scores.

You can add number field to your form and set Min Value and Max value for that field. 

Than you can use workaround provided by my colleague on this thread:

https://www.jotform.com/answers/641041-Can-we-use-a-Unique-Question-with-a-Quick-Tools-Number-Field 

Hope this will help. Let us know if you need further assistance.