How does round work

Ok so I know how it works, round double in power if another round has been used in the same turn and goes right after regardless of speed. But what I just saw confused me. Its my mega elektross and sneasler vs sylveon and grimsnarl and they tried round first turn but i fake out Sylveon. So sneasler is very obviously faster than grimsnarl so I click dire claw into sylveon only for grimsnarl to outspeed my sneasler?? No trick room or speed control is in play so thats why im confused. My sneasler is mad speed jolly so is there like something to round that makes it go first cause its an attack it wouldnt have prankster priority.