understanding fields in cyrus.header file

[Gavin McCullagh]

Hi,

I'm looking at some cyrus.header files while migrating from an old to a new
cyrus-based mail server.  I think I understand it in general, except for
the second last line.  A couple of examples follow:

----------------------------------------------------------------------
Cyrus mailbox header
"The best thing about this system was that it had lots of goals."
        --Jim Morris on Andrew
user.xxxxx^yyyyyyyyy    20756ee342e4c94f
Junk NonJunk $Forwarded Old
xxxxx.yyyyyyyyy lrswipcda
----------------------------------------------------------------------

----------------------------------------------------------------------
Cyrus mailbox header
"The best thing about this system was that it had lots of goals."
        --Jim Morris on Andrew
user.aaaa^bbbbbbb       1b3a81794204b40e
$Label4 $Label1 $Label2 $Label3 $Label5 Junk NonJunk $Forwarded $MDNSent $NotJunk $Junk JunkRecorded $Label7 urgent Old 
aaaa.bbbbbbb    lrswipcda
----------------------------------------------------------------------

Can someone enlighten me as to the meaning of this second last line?

Many thanks in advance,
Gavin