I have translated a great number of those certificates, but because I have never met with the term, I also got curious and phoned the Gangnam Residence Center that issues the document, to ask about it. A staff of the organization said, “it is not an official term used by them, and I also checked with the Military Manpower Administration, 병무청 and received the same answer. They said it seemed like the term was abbreviated and there are only two official terms starting with “복,” which are “복무만료” or “복무만료 소집해제.” So, it means “service term expired.”