Gnus group format line

[Paulo J. Matos]

I am setting up my Gnus and the default format line
"%M%S%p%P%5y:%B%(%g%)%O\n" is given by describe-variable
gnus-group-line-format.

The help is quite useful but at a point it says:
%S    Whether the group is subscribed (character, "U", "K", "Z" or " ")

Doesn't explain what U, K, Z or " " mean at all. Tried to find online
help without any luck.

Any tips or a reference to the explanation?

Thanks,

-- 
Paulo Jorge Matos - pocmatos at gmail.com
http://www.pmatos.net