Purchase order numbering with 3rd Party imported Purchase Orders

We currently are only using EBS Procurement and iProcurement to create Requisitions and Purchase orders. We have setup EBS  Procurement to permit Numeric PO numbers and Automatic Numbering beginning with a specific number. We will soon also be importing Purchase Orders from a 3rd Party system as well as continuing to use EBS Procurement to create Requisitions and Purchase Orders. It is our understanding from reading document 135136.1 and several posts to the Procurement Community that all we need to do is change to Alphanumeric numbering which will still allow EBS Procurement to assign Numeric PO Numbers. Then we need to populate the 3rd Party Purchase Order number in the the Document_number column which will cause EBS Procurement to NOT assign a Purchase Order Number. Is our understanding correct.