Most people can't see those adjustments they're measured with some type of device, usually a particularly made taper gauge of some kind or a dial gauge. In addition to the pinnacle opening, other dimensions of the facing also measured with micro able tools make contributions to its resistance: the contour of the curve among the point where the reed contacts the table
and the mouthpiece tip and the actual length from the tip to the aim where the mouthpiece contacts the table are the main
vital ones. In common, the longer the curve, the less resistant it is. In not unusual the closer the pinnacle starting, the fewer resistant it is. But these can be mixed in novel ways to steadiness or confound one another. Also, there are variable dimensions in the baffle, throat, chamber and even the back bore which could materially add resistance or not and make a curve that are meant to give a distinct resistance level an entire choice feel from what you'd expect.