:::: -- Okay so it the loop finds a file such as C:\folder\path\g123.exe then the below will mean...
set fakename=%%~NXa        :: -- This is the file name only plus extension with no path (e.g. g123.exe)
set realname=!fakename:~1! :: -- This is the file name only minus the first character ("g") on the left plus extension (e.g. 123.exe)
%%~DP :: -- This expands to the drive letter and path only (e.g. C:\folder\path\)


In the answer I put the below details to explain this but it can be confusing, these are for loop substituions

In addition, substitution of FOR variable references has been enhanced. You can now use the following optional syntax:

%~dI        - expands %I to a drive letter only
%~pI        - expands %I to a path only
%~nI        - expands %I to a file name only
%~xI        - expands %I to a file extension only