Dynamic Graph chart

Please check the following link.

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.