1 udn 1 mail

It seems like you're trying to communicate something in a concise manner!

Are you saying:

• "1 udn" means "1 unit" (e.g., 1 unit of something)?
• "1 mail" means "1 mail" (e.g., 1 piece of mail or 1 email)?

If that's correct, could you please provide more context or clarify what you're trying to say? I'm here to help!