In ISO/IEC 15417 specification, the quiet zone of code 128 should be at least ten times the width of the narrowest bar/space element. It is mandatory at the left and right side of the barcode.
Example: BarCode 1
Message : Start B B a r C o d e 1
Value 104 34 65 82 35 79 68 69 0 17
Position: - 1 2 3 4 5 6 7 8 9
Calculate Total: 104 + (34x1) + (65x2) + (82x3) + (35x4) + (79x5) +
(68x6) + (69x7) + (0x8) + (17x9) = 2093
2093/103 = 20 remainder 33
33 = A
Final message: (Start B)BarCode 1(A)(STOP)
To learn more about code 128, please refer to the following passage:
keepautomation.com/code_128/