Chapter 15 Unified Threat Management for FortiOS 5.0 : ICAP : Configuration Settings : Servers : IP address
  
IP address
depending on whether you’ve set the IP version to 4 or 6 will determine the format that the content of this field will be set into. In the GUI it looks like the same field with a different format but in the CLI it is actually 2 different fields named “ip-address” and ip6-address.