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/