How to split channels retaining precise channel colors?



I have an RGB image in which I want to convert each channel into grey layer so I can work on each layer (channel) separately. So I make Channel -> Split channels and it splits my image into three nice separate files but the problem is the grey values, for some reason, slightly differ in those separate files. Even if I select let’s say red channel in channel window, make ctrl+A and copy-pasting it to Layers - I get grey which is slightly different than it was in the red channel. For example - in Channels tab red was 48, but after pasting it to Layers tab it gets 66… You can even try yourself.

What am I doing wrong? How to keep that original value of 48 after copy-pasting? Thanks in advance!