Why does mistakes count so different?

[HyperCloxy]

When I make a mistake in a two-long word like (me) and I do a mistake at the "e" its basically worth -0.4 wpm (2/5 = 0.4) but when I do a mistake in a 12-long word its -2.4 wpm which is not fair. One mistake should always count in the same way. 1 Mistake = -1 CPM I do not understand why making a mistake in a long word is worse making a mistake in a short word, its one mistake and one mistake = one mistake, giving them different values feels weird or am I wrong? WPM = CPM / 5 and nothing else thats how it is defined and 1 Mistake = -1 CPM and not -2.4 wpm or -0.2 or minus something else.

Or is there any reason why you give mistakes so different values? Please tell me, I dont get it!