[syslog-ng] dropped log?

Hello, i am testing syslog-ng on a server which will be used to collect logs from different devices on our network, at this point the server is not busy at all and no outside device is sending syslog to it, i enabled stats_freq() in the global config last night and just now i notice there are 5k logs got dropped since then, see below Aug 14 08:32:59 test syslog-ng[14059]: Log statistics; dropped='pipe(/dev/xconsole)=5093', processed='center(queued)=2795', processed='center(received)=705', So what exactly does "dropped='pipe(/dev/xconsole)=5093'" mean? The load of this server is not heavy at all, i guess most of these messages are firewall logs, why so many logs got dropped? Thanks!