I just bought an Agfa Silette-LK, but don't know how to change ASA. Its on the lens but the dot seems to be stuck on 12. It goes up to 800. My film is 400 ISO. I know it will look terrible unless I set it to 400. It looks like there's a small latch on the bottom, but I haven't seen one like it in Youtube videos for this "Silette-LK" which has a body more like Optima 1a.