Resolution:
stat_msgs and stat_size provide the number and size of messages sent from/received by a producer/consumer for the lifetime of this producer/consumer.
It will be shown in the monitoring message when a producer/consumer is destroyed.

Example:
=======
c:\tibco\ems\7.0\bin>tibemsmonitor.exe -user admin -monitor ">"

2014-08-19 11:43:04.007 [EMS-SERVER] $sys.monitor.producer.destroy
    conn_connid       = long:    18
    conn_hostname     = string:  'host'
    conn_type         = string:  'generic'
    conn_username     = string:  'anonymous'
    event_action      = string:  'delete'
    event_class       = string:  'producer.destroy'
    JMSXDeliveryCount = int:     1
    server            = string:  'EMS-SERVER'
    stat_msgs         = long:    10
    stat_size         = long:    10870
    ....

====