Remote Ping issue with MailChimp

I'm having an issue with Remote Pings on our site.

Basically, everything with the MailChimp integration is working right - except the double opt-in message is coming from the wrong list(!)

In the screenshot attached, I have verified every setting, and the "ID" number is for the right list - so how the message is coming from a different list in the same account, I have no idea.

Any help here?