Hi,
The output tells you the incoming message volume received by MARS.
MARS is receiving a total 2,000,000 messages, and out of this, the incoming message rate per second is around almost 254 (253.930710).
The average message rate per second within a given period is 259.878261.
This figure corelates with the number of Reporting Devices you have in the network, and type of source of messages used to send logs to CS-MARS like syslog, snmp & NetFlow (for Cisco boxes).
Rgds,
AK