Device number simply shows you where you are on the device list. Click "next" and "prev" to scroll through the list.

SNMP managers that traps should be sent to are listed here. The IP address is used to send the trap message. The local name is simply used for display purposes locally.

You may leave the IP address set to 0.0.0.0 and enter a domain name instead. The nameservers identified as DNS1 and DNS2 in the System->Setup->Network page will be used to try to look up the IP address by host (domain) name.

Traps, when enabled on the Trap Enable page, are sent to one of three "groups". The IP address shown here may be a member of one or more groups. If a trap is to be sent to a particular group, all members of that group will receive the trap.