Sign a name with ASCII characters or in my native language?

Question

I submitted some patches for GNU software, and its maintainers accepted them.
They want me to assign the copyright to the FSF, so they sent me a legal document.

Here is the text at the end of that document (and a picture):

Thank you for the contribution!
Signed:                                   Accepted by the Free Software Foundation
     (Chinese name 谢骐,
       or ASCII characters Xie Qi?)
________________________________________  ________________________________________
Xie Qi                                    John Hsieh, Deputy Director

Date                                      Date
          SPELL OUT THE NAME OF THE MONTH WHEN WRITING THE DATE

Q:

Should I sign my name that has the force of law in my country,
or just ASCII characters as indicated below the line?

If both are OK, which one is recommended? What's the reason? Why not recommend another one?