When printing serialized RFID labels that contain GTIN/UPC information, MarkMagic PI can automatically create and keep track of the individual serial numbers generated for each GTIN/UPC value.  The Display Last Serial Numbers menu shows a complete list of GTIN/UPC values that have had RFID tags printed for them along with the last serial number associated with that GTIN/UPC.  This is a just a display list and you cannot edit the serial numbers directly.  MMPI will automatically increment the serial number when an RFID tag is printed for a GTIN/UPC.