Updating asset quantities after data conversion in a new implementation

Hi, I have a Q around using Original Item Quantity and Current Item Quantity fields on an Asset Master record.  The client has two asset systems, one that holds financial information and the other one that holds asset attributes. Now they are unable to link the quantities (as of now) to the asset master records they will be uploading during Go Live. So the asset master records will all be uploaded with Original Item Quantity and Current Item Quantity, both as "1". Now later on when they will have information about the actual quantities, how can that be best accommodated in