I've only ever known it as a counter shaft sprocket but output shaft works as well. .. I'm in the USA so our ways of describing it may be different. Perhaps you folks have less terrain where a little more oomph is useful while going up steeper hills. Here in the States there's a lot, especially in the Eastern and Western parts. Have to disagree with " settling " with what you have. A tooth or two less on the counter shaft makes a world of difference in pulling power up steep terrain. While the HP is unchanged the pulling power is increased dramatically. Obviously, it's easier to go uphill no matter what the terrain. Common practice here in the States.. Some guys also increase the teeth on the rear sprocket as well. If one lives on flat ground area, you might go the other way ( less output shaft teeth ) for more speed.. but for me, I wouldn't have bought the dual purpose XT 250 if that were the case..
*** guess I should have stated in the beginning I'm mainly talking dirt bike riding hills, some fairly aggressive in soft dirt, not street hills. Even so, the principle works the same.