We're assuming someone did a hardness test ( grains of hardness) when the unit was installed. That number can change and softner can be adjusted to the new info. Hardness setting just determines capacity of your softner, lower the hardness number the longer between regenerations ( assuming this is a on demand system), when regenerating you use a brine solution (salt). No matter the number you will get that slimey feeling as long as the softner is doing its job, looks as though it is, you have HARD water.
This has been a quick explanation.
The slime is not residual soap, thats how your skin really feels without hard water deposits on it
wookie