Each record affecting stock levels has an attribute indicating whether the quantity refers to a packed amount. This attribute is called packing. In the user interface, the packing attribute has to be supplied by the user to indicate case stock.
Frequently the packing is always the same for a particular product and the user does not necessarily know the correct packing for all products. The standard packing (or Std Packing) is a default value associated with a product. The standard packing for a product is copied to the packing attribute for a record by entering the letters "cs" with no specific packing (the letters "cs" simply mean use the default value).