Selecting Specific WordPress User Roles to Sync with MailChimp

Dear WMPU Dev,

My client owns a vineyard and has various WordPress users - two member levels, customers, and site admins. (I use a plugin called User Role Editor to create these custom roles.)

They would like to sync their 2 WP Member levels with their MailChimp Wine Club list. I see that I can sync existing users, but will it sync ALL my users (including customers) or just my wine club members?

Thank you!