In Item Search, if you don't type 49 before the DPCI, it will search for the DPCI and give search results instead of just going directly to that item. 49 is like an "adapter" that turns the DPCI into a UPC. When you scan a UPC, it goes directly to the item rather than searching for it. I'm not sure what the reason is in RF Apps though (maybe just consistency, for all I know). If you look at the barcodes for some Target brand items, you'll notice that the UPC is 49+DPCI+[random dummy number at the end].