How to reduce the amplitude of stepper modulation in the sampler?

I like using the stepper in the sampler to provide random values (by randomizing the points) for each trigger.
However I don’t understand if I can lower the amplitude of the modulation.

In fact what I would like is having the stepper act as bipolar modulation with controllable amplitude (lower is negative, upper positive, and middle is null).
Is that possible?

For bipolar,unipolar conversion,the formula is based on

output = input (/ or *) 2 (+ or -) 0.5

Something like that…This is a good approach

maybe someone who have done it on renoise will have a better formula

My brain is out of energy today

(PS:It seem that there is a connection between Renoisers…Yesterday I have begin to think about a parameter randomizer via “formula”…A form of “perlin noise”)