From the initial instructions.
Shoot from any way you desire as long as there is no support other than your body parts. So no bi-pods, tri-pods, cross sticks, or sand bags.
So could be shot standing, feet supported by the ground.
Or sitting, hind quarters supported by a chair.
Or kneeling, knee and leg on ground, elbow on knee.
Or prone, belly and elbows supported by the ground.
So sitting elbows on a bench seems to fall into the "any way you desire" category. At least that is how I took it. Just nothing else like bi-pods, sticks, sandbags contacting the weapon.
But I could be completely wrong.
I shot standing, holding gun in hands, but resting back of left hand against a post. And still probably in last place.