Adding First Name and Last Name to Pings to Mailchimp

Hello:

I have got my remote pings working well except for a user's First name and Last Name, which do not appear in Mailchimp.

The user's first name and last name do appear in the Users Profile.

Is this the correct format?

userfirstname=%userfirstname%
userlastname=%userlastname%

Best,
Michael