Variables defined as OPTIONAL in scope can be used in multiple sections of a policy, but only once within the Declaration section.
OPTIONAL variables are assigned to a default value. These values are not initialized; they are set only if a value is not passed. If a WAN policy request does not pass a new value to the parameter that matches in both name and type, the value defined in the Declaration is used when processing the policy.
You must assign a value to variables defined as OPTIONAL in scope. Therefore, since TIME and NETADDRESS types cannot be initialized in the Declaration section, do not use OPTIONAL scope with these variable types.