Soapui and hash/digest

Soapui when asked produces a timestamp in this format:

<wsu:Timestamp wsu:Id="TS-7"><wsu:Created>2014-08-04T15:30:13.704Z</wsu:Created><wsu:Expires>2014-08-04T15:30:28.704Z</wsu:Expires></wsu:Timestamp>

When soapui is requested to sign the timestamp, what does it use for the hash/digest? Does it use

This: <wsu:Timestamp wsu:Id="TS-7"><wsu:Created>2014-08-04T15:30:13.704Z</wsu:Created><wsu:Expires>2014-08-04T15:30:28.704Z</wsu:Expires></wsu:Timestamp>

or this: <wsu:Created>2014-08-04T15:30:13.704Z</wsu:Created><wsu:Expires>2014-08-04T15:30:28.704Z</wsu:Expires>

or some other part of the timestamp?

I'm trying to find out what part of the timestamp soapui uses for the hash/digest.

Thanks