Can anyone tell, From where this Digest value Coming from?

Question

<Signature xmlns="http://www.w3.org/2000/02/xmldsig#">
<SignedInfo>
<SignatureMethod Algorithm="http://www.w3.org/2000/02/xmldsig#dsa">
</SignatureMethod>
<Reference URI="cid:body@f6a3323c-7c7b-4a5f-b0ed-b3f63a200893">
<DigestMethod Algorithm="http://www.w3.org/2000/02/xmldsig#sha1">
</DigestMethod>
<DigestValue>XU9yAzfwEPuP7L5iOcQY9XRNEWM=</DigestValue>
</Reference>
</SignedInfo>
<SignatureValue>ZxvFMInWLSb1+iNj5xA/OhPHE4uzIx4nXOCmoOyGSSyHWEuODsByooS00j9RsMuGN/FmpEEOgJ1NFCBEDaBAag==</SignatureValue>
</Signature>