3x9 means the magnification like he said. That means you can adjust it from 3x magnification all the way up to 9x magnification or anywhere inbetween. So a 4-16x40 would be the same only 4x to 16x in the magnification department. The 40 part or 50 or 32 or whatever it says is like he said in mm the diameter of the big end of the scope. I don't think you can have a 3x9x1. You might have a 1x32 or something though which would mean it's a fixed 1x magnification. Or a 4x32 which would be fixed on 4x magnification and you can't adjust it.