With any setting, if the turns on your actual wheel are the same as the ingame wheel, then it will do nothing. It is a more intelligent solution than the non-linearity setting (SCR) that mouse drivers have.
At a setting of 0.0, your wheel always translates linearly to the ingame wheel, but the rotation of your wheel could be completely different to the ingame wheel (i.e. turns lock-to-lock).
At a setting of 1.0, if you have more lock on your actual wheel, the response will stay linear but speed up so that when you have turned as far as the ingame wheel can go, the extra turn on your actual wheel does nothing. If you have less lock than what the ingame wheel has, then at the centre position, the sensitivity will be reduced so that it appears that you really had enough lock, but as you apply lock, the steering works in a non-linear fashion so that both wheels reach maximum lock at the same time.
Clear? :S