what is IssuerSerial in xml

XML and business rules
1

in XML (Standard) :

<xades:IssuerSerial>
<ds:X509IssuerName>CN=PRZEINVOICESCA3-CA, DC=extgazt, DC=gov, DC=local</ds:X509IssuerName>
<ds:X509SerialNumber>512917454472782251675574865384895215462051048</ds:X509SerialNumber></xades:IssuerSerial>

what is this Values ??

Please Dont Tell me Check Electronic Invoice Data Dictionary.xlsx because its not there