When you click into a referral source on the Registration Referrals report, a Registered Users pop-up opens listing everyone who registered through that source, with columns for User ID, Full Name, Other Referral, and Registration Date. If a customer typed in free text when registering (for example, picking "Other" as their referral source and describing it), that text is stored per-user and shown in this column next to their name; otherwise the column is blank.