Board Thread:M.U.G.E.N Help/@comment-26422286-20150522005246/@comment-3495717-20150522125427

It should be 2/3 rounds by default, but yes, there is a way to change it.

Open the fight.def you screenpack uses and look for [Round]. Underneath that should be match.wins = 1. Change the value to however many rounds you want to be won before the next match.