Pasting into a layer mask changes values

[Guest]

I have a grayscale image in a layer and another layer with a blank / white mask applied. I copy the grayscale image and paste it into the mask, and find other grayscale values, which is a no-go for a software developer. I did not choose the values for fun but because I need exactly these and no others (99% black/RGB 1/1/1 is 100% after pasting / RGB 0/0/0).

I tried it with another document, and by converting everything from RGB to grayscale, but it didn't change anything on this behaviour.

[Stephen Marsh]

https://community.adobe.com/t5/photoshop-ecosystem-bugs/how-do-i-write-a-bug-report/idi-p/12373403

What is the version and build of Photoshop?

What is the version and build of Windows?

What is the document colour mode and ICC profile?

What are the exact steps to reproduce the issue?

Curious if the Apply Image command works as expected.