I have a Contax iiia and 21mm Biogon f4.5 lens. When the lens is mounted the red dot and the black arrow focus index marks are not at top dead center but are off to the right (looking into the lens) a little. Not all the way to 1:00 but at about 12:30. Is this how the lens should mount? I would expect the red dot and focus index to be precisely at the top but I've never had one of these before.