trying to perform a fill rate analysis

We were given two separate spreadsheets
1. Line Item Orders
2. Customer Shortages

was told to use =order&"-"&item on in both sheets

Then =IFERROR(VLookup(order/item,CustomerShortages,2, False),Order/item)

There are approx 113000 lines on the Order sheet and only ~6000 on the shortages. I have the IFERROR formula on the order sheet and reference the shortages for ordered and shipped information. Yet all 113000 lines have something on them.

What am I doing wrong?