[syslog-ng] mark_freq() wrong?!

[Wolfram Schlich]

I am using this in syslog-ng.conf:

 options {
  mark_freq(300);
  stats_freq(600);
 }

Strangely, the MARK lines appear every 10 minutes (600s) instead of
300s.

Any ideas on that?
-- 
Wolfram Schlich