The last bit is the inspection code.

For example:

The barcode number is 9787307045590, of which 978 refers to China.

Starting from the fourth digit, each digit is multiplied by the second inverted digit in descending order from 10, and then summed. Namely: the fourth digit 7 * 10 =70, the fifth digit 3 * 9 =27, the sixth digit 0 * 8 =0, the seventh digit 7 * 7 =49, the eighth digit 0 * 6 =0, the ninth digit 4 * 5 =20, the tenth digit 5 * 4 =20, and the tenth digit 5 * 4 = 20. 2 = 18 (9 is the penultimate number of barcode number) and =2 192 19 divided by 1 1, and then take the complement of 1 1 as the result./kloc

ISBNNo.: 730704559 1.