Let me guess you are using gamanilia host or whatever name it is
They diff their clients to read custom client.xml which they locate it at book folder 7372.txt or something and they fill the top of the file with lots of unknown characters to make it looks like any other file in book folder
So the purpose of it keeping your client.xml details safely <<- atleast what they say
Nothing suspicious there,
And I am assuming the main.grf they provided you is a translated grf , which is normal again
If you want to use your own client and your own grf ,
1. diff your own client
2.modifyclient.xml
3.update your new client version in Server side
4. Add your custom grf name in data.ini