적다 is writing something down — filling in a form, jotting a note, captioning a picture — and 라고 marks the exact wording: 2학년 때부터는 가수라고 적어 왔던 것 같아요 'from second year on I always wrote singer', 사슴인데 저는 곰이라고 적었는데 'it's a deer, but I put bear'. Against 쓰다 'write', 적다 leans toward entering or noting something rather than composing it.