Starting The Seated Press

You might use the back support provided with the bench to get some rest.

But, as soon as you are ready to move the bar from the rack there is nothing better than getting your own back to stand alone without seat support.

You are just sitting not leaning backward.  Even if you start with very light weight I recommend that you dismiss what you see in many junk magazines and fitness books that state otherwise.  Leaning backward on the back-support board is the commonest mistake you see in today's Gym.