From the Target Clearance Thread OP:
DPCI stands for Department, Class, Item-- it's Target's version of a SKU. These are a nine digit number that can always be found on your receipt and also on the red clearance tags on the item itself. DPCI numbers are handy to have when you want to check the item's price-- just go over to your scanner and punch in the numbers, if your scanners have keypads. Also, you can give these numbers to team members so they can check the availability of the item easily with their PDA scanners.