[syslog-ng] question regarding program name logs

Hello, I am currently using Syslog-NG version 2.0rc1. I've noticed that sometimes when Syslog-NG is logging messages, it prefixes something onto the program name which disrupts filters while matching against a program name. For example, in some logs for a program named "foo" I'll see logs in the form of "<15>foo" which fail to be matched against a filter of 'program("foo") '. This seems to only be noticed on logs which originate from remote hosts. Could anyone provide an explanation for what is going on with this? Regards, Justin Randall