Limited amount of log data

Hi,
Trying to set up xymon to capture log data. Once I changed the permission
on the var/log/message file, I got -some- data. I am taking the defaults
with xymon 4.2.3. I might appear that I only get to see the last 30 minutes
of log data. Can this be increased?

Second, why does it say No entries in /var/log/messages.
Thanks.
System logs at Thu Mar 5 17:03:20 EST 2009


No entries in /var/log/messages


Full log /var/log/messages
Mar  5 16:56:00 tcdcpega syslog-ng[1494]: STATS: dropped 0