Why is CSK's Dwayne Bravo wearing jersey number 400 vs MI?

Chennai Super Kings all-rounder Dwayne Bravo is wearing the jersey number 400 instead of his usual number 47 in the IPL opener against Mumbai Indians today. Bravo had become the first bowler in T20 cricket history to take 400 wickets in December last year. The 34-year-old had revealed he would wear the jersey number 400 just for the opening game.