How to adjust "Maximum Concurrent Poller Processes"

[areast]

HI ALL

Since changed snmpv3 and found some of the devices could not polling (status down) as I tested snmpv3 is work fine between server to devices
However I fix some devices by changing "Maximum Concurrent Poller Processes" value. So i guess this is the issue to cause some of the devices timeout to get snmpv3
Just want to know how to set below value correctly

Under Setting -> Poller
"Maximum Concurrent Poller Processes" (Current 40)
"Maximum Threads per Process" (Current 80)

under Devices
"Number of Collection Threads" (Current 1)
"Maximum OID's Per Get Request" (Current 10)

Using with Windows 2008R2 64bits (VM) 8CPU x 12GB RAM
Using CACTI 0.8.8c (Poller Type cmd.php)