What does "E2" and "E3" stand for in a program listing?

[4ster]

Sorry, I wasn't clear.

Entering "APPEND" on the 41 keyboard isn't my problem. I am copying text from the library on this site and inserting it on a web page that generates barcode. The page does not supply documentation about how to enter a line of appended text. For instance one line in question is:
08 "~M" ( append M )

The web page does not recognize "~" as APPEND.

I am not finding the author's contact information on the site.

Thanks for all the help.