Hi Arockia,
Cumulative time is the sum of durations for all hits of one request on the selected period (current day by default). An example, is the cumulative time of executions of the request "select * from user where user_id = ?". Then the report displays a percentage of the cumulative time for this request compared to the cumulative time of other requests such as "delete from user where user_id = ?".
The total started count of threads is the number of threads which were started since the JVM was started, for http connectors, application threads pools, caches management, short live background tasks ...
Most of the time, many started threads have finished and have died. That's why the current count of alive threads is often much less than the total started count.
bye,
Emeric