When checking the Syslog server, some messages are missing compared to viewing them through ProxySG Event Log.
 

The logs that are missing are internal ProxySG logs. Internal ProxySG logs are not sent to the syslong server. You can identify internal ProxySG logs by checking if the number 64 or 65 appears after the colon in the log, for example:

2015-10-07 07:28:10-00:00UTC  "Console agent unable to respond to network request, no HTTP request data"  0 60002:65   cag_agent.cpp:440

Currently there is no resolution or workaround for this as this is expected behavior.