OL Learn

Barcode module width

What is happening with the module width of Code128 barcodes?
I tried changing the module width of my barcode in order to change the total size of the barcode, but it seems to be rounded or truncated before the barcode is calculated.
In this image the same barcode is repeated with the module width changing from 0.01 by 0.01 steps. The right hand edge should form a straight line. When the value is 0.05, the barcode is undersized and when it is 0.08 it is oversized.

Entering a value with more digits (eg. 0.032) always gives one of these sizes, showing some kind of rounding is happening.
I have had to use scaling to get the barcode size that I want.