In monotype match (Me = Psychic, Him = Fire)

Me: Jolly Meloetta Piroette (Speed = 390)
Him: Charizard (Max possible speed = 328)

He tricked a choice scarf onto me earlier, making my speed * 1.5
Switched into Charizard, takes stealth rock, yada yada

First turn -> I drain punch him, take out a quarter health
He uses dragon dance -> Makes his speed * 1.5

Second turn -> He outspeeds me and uses a second dragon dance
I drain punch for the kill

How does a Charizard with only +1 speed outspeed a Scarfed Jolly Meloetta? I'm not particularly complaining because I still won the match, but that's not entirely possible...