This is good advice. There may be times when you want bar code as small as possible, however, this is only true until it becomes less readable. You must then weigh the difficulties that may be encountered when reading the bar code against the advantages of having smaller bar code. Even then this should be done only when the printing techniques are controlled and of sufficient resolution to get the tolerances necessary. Readability vs Scannability Bar Code Pro will help you to optimize the quality of the bar code you create, both in terms of readability and scannability.
Readability is the measurement of how well the symbol is interpreted.
Scannability is a measure of the ease with which the scanner can decipher the symbol. For example, if two symbols were equally readable, a tall symbol is considered more scannable than a short one because there is a greater chance that the scanner will see the taller symbol. Likewise, two symbols that are equally scannable may differ in readability due to the narrowness of the symbols or the quality of the printing. The specifications that affect the readability and scannability of a symbol are width, color, printer dpi, bar width reduction, reflectance, and contrast. Symbol height only affects scannability.