Extra|Sort Alphabetically Z-A works just like Extra|Sort Alphabetically A-Z, except that the file or the selected text is sorted in reverse alphabetical order.
Alphabetic sort works on a character by character basis, even for numbers. “A4” reverse sorts before “A19” because 4 reverse sorts before 1. Use Extra|Sort Alphanumerically Z-A, 9-0 if you want numbers to sort logically.
Extra|Sort Alphabetically A-Z
Extra|Sort Alphanumerically 0-9, A-Z
Extra|Sort Alphanumerically Z-A, 9-0