We recently started using Nintex forms and maybe this is far too simple of a question but I didn't see anything when I searched for Content Type for list forms so I figured I'd ask.

Exactly what is the above required field expecting and what should be entered there for a custom list? What are the valid types and IDs its looking for here? When we used SharePoint and InfoPath it just asked for the SharePoint list and pulled the InfoPath form from there. This really complicates the process.