Question about filament sensor

[Tinchus]

Hello. I have installed an encoder as filament sensor. It has a whell with 100 holes so should be pretty much precise.
It is working. Im on the stage of fine tunning it.
this weekend I have had a "false" filament error. I say false because I checked and there was no jam/cog/nothing.

This is the result of the command M591 D0 I executed when I saw the printing paused:

M591 D0
Pulse-type filament monitor on pin io2.in, enabled, sensitivity 0.292mm/pulse, allowed movement 80% to 140%, check every 2.0mm, measured sensitivity 0.293mm/pulse, measured minimum 78%, maximum 113% over 8668.6mm

After resuming and some mms of filament extruded, the same command gave me this:

Pulse-type filament monitor on pin io2.in, enabled, sensitivity 0.292mm/pulse, allowed movement 80% to 140%, check every 2.0mm, measured sensitivity 0.292mm/pulse, measured minimum 96%, maximum 105% over 110.9mm

The ast result is pretty much the same values I was watching while doing the forst test. This is the first time I lauched a long print.

So as you can see the minimun and max values measured is like they grow over time.

Why is that so? It is an acummulation of measuring errors? I though the measuring was done each 2 mm of filament and then the measuring started all over again, but I can read the measuting was done over 8668 mm of filament.

For example, after 20 minutes I get:

M591 D0
Pulse-type filament monitor on pin io2.in, enabled, sensitivity 0.292mm/pulse, allowed movement 65% to 140%, check every 2.0mm, measured sensitivity 0.292mm/pulse, measured minimum 94%, maximum 108% over 406.3mm

Minimun measures has gone down to %94 and max measures has gone up to 107%

My board is a duet3 + sbc firmware 3.4.5

My configuration command is:

M591 D0 P7 C"io2.in" L0.292 S1 R80:140 E2 ( have changed it now to M591 D0 P7 C"io2.in" L0.292 S1 R65:140 E2)

Update: 3 hs later:
Pulse-type filament monitor on pin io2.in, enabled, sensitivity 0.292mm/pulse, allowed movement 65% to 140%, check every 2.0mm, measured sensitivity 0.293mm/pulse, measured minimum 86%, maximum 128% over 2352.4mm

Minimum and max measured values continues to increase/decrease

Thanks in advnace