Hiding last name field

Hi
I’ve changed my mailchimp form to hide the last name field (rather than delete it, so as to not lose old audience data). The lastname field is marked not required in the mailchimp form.
But the mc4wp form shows the last name field, and it seems it’s required, even though when I click on the last name button, it says it’s not required. But the code below says required. Here’s how it looks:
http://prnt.sc/v3rzr2
How can I:
1. hide last name
2. make it not required
I thought the mc4wp form mirrored the mailchimp form?
Thank you!