2 600W lights means 2 ballasts, eh? You need 2 triple plugs. One plug into the wall socket and the other plug into the timer. NOTE -- do not plug lights/ballast into timer before you set up the timer. Nothing burns out bulbs quicker than flipping them on and off. So use a small lamp or a drill motor to set up your timer. Rotate the timer until you approve the action, then plug ballasts into timer.
Good luck, BigSteve.