Dynamic Graph chart

Guys
Please check the following link.
http://www.notestips.com/flashchart1.html

if you click on update chart, you will see the bars setting up as per the field value.

this guy who created the chart has given a maths equation to set the bar height according to field value.

duplicateMovieClip(“y”, bar, m);
setProperty(bar, _width, Number(Lenght)/Number(NoOfValues));
setProperty(bar, _x, Number(getProperty(XAxis, _x))+Number((2n-1)/2(Number(getProperty(bar, _width))+10)));
setProperty(bar, _height, (eval(“y” add n)/max)*Hight);
setProperty(bar, _y, Number(getProperty(yAxis, _y))-Number(getProperty(bar, _height))/2);

Since i am not that familiar with actionscript, i am confused how he calculates the bar height.

he has taken the major source help from flash kit tutorial, dynamic flash chart.

I need a simple code to calculate the bar height.
thanks for your help.