How to use Duration for Attribute Customization?

According to https://jazz.net/library/article/537 the type of the attribute customization should match the type of the attribute.

I want to define a default value for an Duration type attribute but that is not possible to select in the Process Configuration / Attribute Customization / Add Configuration Dialog. Why isn't Duration listed along with the other types?

Is there any other way of adding a default value for a Duration type?

I am running the Eclipse RTC client:
Version: 3.0
Build id: RTC-I20110307-1844

The server is of version 3.0.0 iFix1

/BR Peter