Don't recall the exact numbers, but shaving a pound of weight off the ship means about a pound less fuel needed to reach orbit. That 2lbs less weight meant the motor needed to produce 2lbs less thrust. That equals a smaller capsule, a smaller fuel tank and a smaller engine. I recall reading in the past, somewhat tongue in cheek, that one less cheeseburger consumed, shaved 10lbs off the total vehicle weight.