#14 is a thicker thrust washer, whereas #15 is very thin and fits under the circlip on the end of the mainshaft. There were three thickness options for #15, a 0.1mm, 0.3, and a 0.5mm very thin but none of which are available from Honda anymore. The one in your hand I expect is a .5mm. Keep in mind there needs to be a slight amount of end play on the mainshaft. I believe they state 0.004" maximum end play.