From Urban Dictionary via Infectious Greed comes this handy term Banker’s Dozen :

Banker’s Dozen

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December 15, 2011 Urban Word of the Day The opposite of a Baker’s Dozen where the customer receives 13 of a product for the price of 12; in a Banker’s Dozen the customer receives 11 of the product for the price of 12 Hector was surprised to find only 11 glasses in his gift of 12 glasses that he received from the bank. Later, Hector learned that the Bank offers a Banker’s Dozen in their gifts and products, in which they steal one item.

I am pretty sure nearly everyone has experienced that at the hands of their own bank at one time or another …