DDNS without using FortiGuard DNS servers

Found a post showing these commands to setup DDNS settings through CLI can someone explain each command please...

specifically the edit 2 - what does the 2 stand for?  set monitor-interface "internal4"?

config system ddns         edit 2         set ddns-server dyndns.org         set ddns-domain "hostname.dnsalias.com"         set ddns-username "youruser"         set ddns-password xxxxxxxxxxxxxxxxxxxx          set monitor-interface "internal4"     next