Candidate referred by Agency on a job application shows Source as Email and Agency on general profil

A Candidate referred by Agency on a job application shows Source as Email and Agency on general profile. How is this source 'Email' coming on job application when the candidate is referred by agency. ? Similarly Agency referred candidate shows Source as 'External career site', 'Google' and 'Vendor' on job application. We want to understand how these sources are being picked up.