In your case, I would just enter the name of the country. There was a report of someone whose issuing authority was something like "KX007FFWX", they entered this in the place of issue field, and the application was canceled.
Exactly, upload a detailed letter with legal references instead of what they are asking for. Anyway, you can't provide what they're asking for, and it's an unreasonable request considering you're applying for a DTV.