440 initial timing mystery

ok now a final piece of the puzzle, i marked TDC using a camera scope at piston 1 i cranked till the piston reached the top then notice the piston stayed at the top for about 6 degrees of being turned i divided it by two and well marked it which came to be 10 on the damper. Would it be possible then that true TDC is when the piston reaches the top the first time or when its divided by two? remember this is a visual examination suing a scope