App error message: Enter in 6 half-width numerals

If you're trying to use the Di2 E-Tube Project mobile app, you might have run into this cryptic error message regarding half-width numerals...

Enter in 6 half-width numerals

What does it means? I have no idea, to be honest... but what the app is trying to tell you is this:

You need to use a 6-digit passkey. You have probably used a four or five digit passkey, and that doesn't work. All Di2 passkeys / passwords are always six characters long.

six half-width numerals

If that doesn't help, send me a message and I'll do my best to help!