list_uuid: "MFXXXX", //The UUID of your list
subscriber_id: "sub_123ABC", // Subscriber's ID
response: "new_registration",
name: "John Doe", //Subscriber's name
extra_field: "+1 2348891123", // Subscriber's extra field's value
extra_field_2: "USA", // Subscriber's second extra field's value
code: "2hg36dvs", //Subscriber's unique referral code
source: "facebook", //Subscriber's source. If the subscriber doesn't have a source the value will be "direct_visit"
}, //This property can have 3 possible values: an empty string (if the subscriber has not been referred), an object containing data of the referral (if the subscriber has been referred) or "subscriber_deleted" (if the subscriber has been referred but the user has been deleted.)
referral_link: "http://mywebsite.com/LINK_PLAIN",
people_ahead: 2873, //number of people in the list in front of the current subscriber (Only for Waiting lists)
created_at: 1234567889 // Timestamp of the subscriber's sign up