I'm setting up a registration form for signing up for classes - and need to cap a class at a certain number.

i'm setting up a registration form for signing up for classes - and need to cap a class at a certain number.  How would I do that?  Can I edit the form once the number has hit to take the class off?  or can I somehow make it stop taking registrations after a certain number?

You can limit the submission to your form in the Form Status section. Here's a screencast guide that you can follow:

1. Open your form.
2. Go to the Settings page.
3. Select the Form Settings tab.
4. In the Form Status section, select the Disable on submission limit and see what options you want.

To edit the form submissions, please check this guide: https://www.jotform.com/help/325-How-to-Edit-Submissions-Made-on-Your-Forms

Is that what you're looking for? If not, please let us know. Thank you.