What algorithm is used for CMYK component extraction in gimp 2.10?

[leopardyao]

Dear Experts,
My gimp version is 2.10.22
For one of my project ,  I can see high contrast when I extract the "cmyk Yellow" component of the image.
I did this through colors-extract componet.

However if I try to recover this in other software or in programming,  the result differs.
For example, for one of the pixel value RGB= (150，136, 146) in my picture.
if I use gimp, the yellow channel gives pixel value 15.

But if I follow the popular formula here: 
https://community.adobe.com/t5/color-man...-p/1884317
or similarly follow the gimp github source code, gimp_rgb_to_cmyk
https://github.com/GNOME/gimp/blob/maste...lorspace.c
I got sth different:
CMYK percentage
0.0, 0.09, 0.03, 0.41
in 255 it is: (so yellow channel is 6)
array([  0,  23,   6, 105], dtype=uint8)
I tried to adjust the pullout but it seems not easy to get gimp CMYK results  matching with formula o

I do undestand there is no general formula between RGB to CMYK and sometimes icc profile is needed.
So the question is , what kind of algorithm is behind GIMP "CMYK yellow" channel extraction, is it by some icc profile? if so which? or if there is some gimp formula?

Thank you very much!