MIDI NRPN resolution, NRPNIN, I would like to understand ?

Hi I'm looking to use NRPN MIDI messages to benefit of the 14bit resolution in order to convert it in CV voltage for my eurorack and having the finest voltage control under my fingers :)

I want to use a Behringer BCF2000 as an NRPN controler and creating a max MSP patch to translate fader motion in CV voltage by the ES3 Expert Sleepers module.

I'm at the beginning and i have a question about the NRPNIN object.

When i observe the parameter value (the leftmost out NRPNIN) going out with Max console i'm not seing what i'm expecting...

For exemple if i'm programming a NRPN with a 255 steps depth (this is the minimum while the maximum would be 16383 steps) i can observe when i move the controler fader a step interval of 2 (0 2 4 6 8 ..... 254 255). So the "bit depth" is not 255 but 255/2=127... ?

And more i increase the NRPN steps depth more the interval value increase when i'm observing the incomming NRPNIN values.

Where i'm wrong ? how to benefit of the NRPN hi resolution values in MSP signal processing ?

If somebody can help, explain, know... i would appreciate a lot :)))