Copy and Paste doesn't copy file permissions. It's that simple!
So, where does it get the file permissions from? Even simpler - the parent directory. You'll note that in your image on the right the ticks are are greyed out - that means those particular permissions are "Inherited". This will be the same for all permissions on that file.
Conversely, the file on the left has black ticks for the "Everyon" group, meaning that the "Everyone" permissions was applied manually to that file and does not necessarily apply to the parent directory.
This is why, even though both files are in the same directory, they have different
You can use Robocopy if you wish to retain permissions when copying files.
One related exception is that it WILL retain custom permissions if you move a file around on the same volume.
See KB310316 - How permissions are handled when you copy and move files and folders