gnus-agent-expire seems to expire more messages than it should?

[Eric S Fraga <e.fraga@ucl.ac.uk>]

Hello,

at some point recently, I realised that my agent directory was using up
over 2GB.  Not a big deal, as such, but I thought I could clean things
up a little.  I had a look at gnus-agent-expire and realised that
expiration of articles did not necessarily clean up the agent cache.  So
I executed this function.  Success: I freed up a lot of space.

However, I seem to have freed up rather more than I expected.  I have

,----[ C-h v gnus-agent-expire-all RET ]
| gnus-agent-expire-all is a variable defined in `gnus-agent.el'.
| Its value is nil
| 
| Documentation:
| If non-nil, also expire unread, ticked and dormant articles.
| If nil, only read articles will be expired.
| 
| You can customize this variable.
| 
| [back]
`----

which tells me that only *read* articles would be expired.  The gnus
agent seems to have expired all kinds of read articles as well,
essentially behaving as if I had set gnus-agent-expire-all to something
other than nil.  Am I misunderstanding something or have I missed
another configuration variable?

I haven't lost anything, obviously, but all my expired *unread* articles
now need to be re-loaded.  No big deal but I am curious!

I am using gnus up-to-date from a day or so ago.

Thanks,
eric

-- 
: Eric S Fraga, GnuPG: 0xC89193D8FFFCF67D
: in Emacs 24.3.50.1 + Ma Gnus v0.6
: BBDB version 3.02 ($Date: 2013/01/13 22:41:36 $)