Going to press is exciting. Lots of hard work is behind you, and the finished book is close to becoming a reality. But as you print your books, you should be aware of potential complications. Consider the printing of your book as a custom project. The jacket, covers, and text are unique–written, designed, and printed specifically for you as opposed to being interchangeable commodities to be pulled from a shelf.
That being said, it's difficult for a printer to produce the precise amount of books you request. When the printer orders materials for printing a book, he must allow for spoilage at each manufacturing stage. If production runs smoothly and spoilage is kept to a minimum, there will likely be higher yields of the final product. These extra books are referred to in the industry as "overs."
And here's where people tend to get confused: Your invoice will reflect the total amount of books shipped from the printer, meaning that if relatively few books have defects, you'll end up being charged for the total number of books shipped.