What is the source of the message body used in PO_PO_CREATED_FOR_REQ for PO Draft email notification

Hi Experts,

When a PO is created, a draft notification is sent to the buyer like the one given below (before submitting the PO).

I am trying to edit the text enclosed in the green box and unable to find the source of this message.
Upon analysis, it is figured out that a event triggers the workflow.

Workflow function: Send Notification to requester found in the Activity: Receive Notify Requester Event has call to PO_COMMUNICATION_PVT.notify_requester

There is no fnd messsage with name PO_PO_CREATED_FOR_REQ.

In WF_MESSAGES table, for PO_PO_CREATED_FOR_REQ, the body column shows &Notification_Region.(HTML). Also, in the workflow as in the below screenshot.