What's the meaning of letters following slash in raw cmds?

The arguments of several raw commands have alphabets after the slash like:

ADD/S
REGEXP/K/M
SET/K

What are these S, K, M etc.? Where can I learn about them?

They're described at the start of the Opus Raw Commands chapter:


gpsoft.com.au/manual9/NetHel ... ommand.htm has:

Shouldn't it just be FILE/M?

Yeah, the /F doesn't mean anything and looks like a typo.