interpreting ipmon log line

From:	"Ryan Wagoner" <Ryan at wgnrs dot dynu dot com>
To:	<m0n0wall at lists dot m0n0 dot ch>
Subject:	interpreting ipmon log line
Date:	Mon, 10 Apr 2006 15:21:40 -0400

Apr  9 06:41:55 jellyfish ipmon[92]: 06:41:55.148489 fxp2 @200:10 p 129.174.172.128,1497 ->
10.10.1.150,3389 PR tcp len 20 48 -S K-S IN

I'm trying to interpret the above log line. What is the @200:10 p part and the ending len 20 48 -S
K-S IN? I'm assuming the @200:10 p is something to do about packets and the ending has to do with
the length. I tried searching google but I can't find anything. I would really appreciate an indepth
explaining or a link to an explaination of the ipmon log line. 

Thanks,
Ryan