What is the purpose of the scale argument in functions such as setYLabelsColor()?

Take a look at below image. There are two lines in there, scaled in a separate way, the "Air temperature" on the left having scale = 0 and the "Sunshine hours" on the right having scale = 1.
_{(source: achartengine.org)}

I believe that scale is meant to refer to which series that you are editing. In a multipleXYseriesrenderer, the scale number refers to the "nth" series you entered. For example, if you only have 1 series, then editing scale "0" will edit only that series. This is what my understanding is, although I cannot say for certain. IT seems that the documentation could certainly use some cleaning up.