It's about internalizing rhythm, so he kind of has his hand playing along with the beat, but by varying whether he lets the notes ring out his playing becomes syncopated.
Try and watch what his right hand is doing, then do that with your hand, then vary the palm muting and your left hand fretting do sound notes at the same time.
Sorry if that's a bit confusing it's quite hard to describe.
How long have you been playing for?