Afaik there is no universal way to handle numbers in alphabetical lists. Sometimes numbers some before letters, sometimes after, etc.
A digit is not a part of the alphabet, right?
But it's actually not ASCII sorting either! ASCII sorting would mean 'Z' comes before 'a' and I assume even the author doesn't want that!
No matter what, there are going to be hidden tricks!
I don't know about the author, but that's exactly what many others who know about ASCII expect, including me. Digits, then uppercase, then lowercase.