The first number segment is the area number, which consists of 1~5 digits, 7 stands for China publications, and the second number segment is the publishing house code, which is assigned by the ISBN center of the country or region, and the allowable value range is 2 ~ 5 digits. The bigger the publishing house, the more books it publishes, and the smaller the number.

The serial number of books in each publishing house is fixed. The shortest one and the longest six. The bigger the publishing house, the more books published and the longer the serial number.