Suppose Radiant takes the first hero kill, but Dire later destroys Radiant's Ancient. Radiant gets first blood and Dire wins the map. A kill lead alone cannot decide the map winner.
Read the team names beside the sides for that specific map. A team can play on a different side later in the same series.
In a best of three, the series winner took one more map than its opponent. It needed a 2-0 sweep to cover -1.5 maps.
More sports: League of Legends, Mobile Legends, Counter-Strike.