Multiple additional names don't show correctly on autoresponder

My form has an option to enter up to 2 additional names (of people you want to register). The autoresponder table assigns both these names the code <additionalname> and duplicates the second name into the first autoresponder fieldof the email - so the first additional name is not shown on the autoresponder.

How do I assign a unique field name so the autoresponder picks up both addittional names

I'm not quite sure if I understood your concern correctly.

Upon checking your form, you do not have an autoresponder setup. You only have one notification email setup:

That notification will only be sent to the email addresses you set in the recipient field.

To learn more about the two types of email alerts that we have, you can check this guide: https://www.jotform.com/help/30-Explanation-of-Email-Notification-and-Autoresponder-Settings 

The email body can fetch any of the input fields on the form, you can get their field tags when you click the "Form Field" drop down menu in the text editor:

In your case, the "Additional name to register" field has a field tag of {additionalName}.

Let us know if you are still having problems on this. You can try deleting your current notification and create a new one and see if that resolves the problem you are experiencing.