Edit PO not appear in PO notification

Dear All,

Question :

Buyer create PO and sent to approver. After approver click the notification and make changes in PO description, then click OK but the changes not reflect in approver notification. 

After that when check in Purchase Order Summary the PO detail already changes.

May I know why and how to make it reflect in notification?

1. Approver notification

2. Click edit Document

2. Update the Description

3. Click OK

4. In PO summary

5. But the changes not appear in approver notification