Issue with Hustle plugin sending fields to Mailchimp

I am having an issue with the Hustle plugin. The plugin is working correctly on my site, however, once the user submits the popup form, the fields are not transferred over to Mailchimp correctly. The First Name ends up in a Zip Code field in our list and the Last Name ends up in the First Name field in our Mailchimp list. I have been unable to find anywhere in the plugin admin settings to adjust where the fields are sent. Please advise on how to fix this issue.