Would you please help me understand backend configuration displaying pxUpdateOpName as below in the clipboard

I understand the email is processed by an agent called 'EmailProcessingAgent' but I am interested to know how the whole strings "[Code-Pega-Requestor.pyUserName]EmailProcessingAgent John Doe"  is derived for pxUpdateOpName.

(in the example above: John Doe is an approver)

Reproducible scenario:

1) Use Approve/Reject Utility in a step 

2) Enable Email Approval

3) Send email request for approval to approver John Doe 

4) Click Approve or Reject in Email and Send Email