The EAN bar code on the back cover of the book displays a set of two bar codes side by side. The first bar code on the left is the EAN, which is derived from the ISBN. The smaller bar code on the right is a 5-digit add-on and often contains the encoded retail or list price of the book. This is referred to as an EAN-5. The first digit of the add-on data indicates which currency the price is expressed in. For US dollars, the designated digit is a 5 so an add-on of 51995 indicates a price of US $19.95.
You may choose not to include the retail price information in the bar code. In that case, the default value for the add-on is 90000, a null code which indicates that there is no pricing information encoded in the bar code.