Signing Generated Timestamp does not work

I have an XML message where I am having SoapUI generate the WS-Security Timestamp for me (WSS Entry). The generation of this seems to work correctly. I also have a WSS Entry for generating a signature. In the parts table I am listing a name of "Timestamp" and Namespace of "http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" and Encode set to Element. SoapUI will generate this element for me along with a signature, however the DigestValue generated does not actually match the content. I have not been able to replicate the digest value created by SoapUI so I don't actually know what it's doing. Is this possible to do? Can I have SoapUI both generate the timestamp as well as sign it for me?

Thank you.