Mailchimp for Formit Single Opt-In

I have been trying to get the STERC Mailchimp extra to successfully add users to a list without having an opt-in email sent to them. I see no setting anywhere to allow for that, so anyone who fills in the form gets the double opt-in email. Is there a setting I am missing? Thanks!

I think the double or single opt-in has to be changed in the actual mailchimp account on their website.

Yes double opt-in is a feature, but is not enabled.