Substitute approver in PO Workflow

Hello All,

We have a scenario where in single person is substitute for for multiple PO approver.

In the above scenario User 03 is substitute  for  2 approver's ,

While forwarding the Email notification system is able to identify substitute for User 01 but not for User 02.

So any notification related to user 01 is forwarded to User 03 but same is not happening for user 02.

Workflow is not able to identify the same Substitute for multiple approver.

How does this functionally work's in standard SAP,Is single person is allowed as substitute for multiple approver & Notification are forwarded.

Please help to resolve.

Thank you.

Manish