-ㄴ가 attaches to a word the speaker is not sure of, and 나오다 is coming out or showing up. Two things happen here. With 뭔가 or 누군가 it means something or someone appearing — 뭔가 나와요? (is anything coming out?), 누군가 나와서 뭔가 딱 정리를 해 주면. With a number or a source it hedges the figure instead: 3천몇백만 원인가 나왔어 (it came to thirty-something million, I think), 연초 한 4월인가 나왔을 때.