The #1 on M Countdown on 2012-05-03 was “Volume Up” by 4Minute — win No. 1 for the song and career win No. 1 for 4Minute (No. 1 on this show).
“Volume Up” has 1 music show wins in total: 2012-05-03 M Countdown. 4Minute had 1 wins in 2012 up to this date, and this was the artist's first win on M Countdown. The previous week's M Countdown #1 was “Alone” by Sistar. Episode data comes from broadcasters' published results (Wikipedia lists, CC BY-SA) and is recounted daily.