Milter-greylist

I've tried adding the parameter "subnetmatch /24" into my
greylist.conf file but it does not seem to be doing anything nor can I
tell it is even being read. If I start in debug mode the milter dumps
out all the parameters from the greylist.conf file but subnetmatch is
not listed. Same thing if I add the /L24 parameter to the command
line. Additionally the IP addresses in the greylist.db file for
greylisted users still have all 4 octets listed as shown below so I
can't tell if it is using all 4 or just the first 3.

For example, If get 2 emails from the same user and to the same user
from the gmail.com domain I can see that both entries are listed as a
greylist tuple. For example:

209.85.146.176  <user@...> <user@...>  1186068847 #
2007-08-02 10:34:07
209.85.198.185  <user@...> <user@...>  1186070455 #
2007-08-02 11:00:55

In this case the subnetmatch probably would not apply since the 3rd
octet and the 4th octet are different but my main question is how do I
know that subnetmatch is even working since there is no indication it
is enabled?

Any ideas?