+1  A: 

little look at google show :

Axis Range chxr : You can specify the range of values that appear on each axis independently, using the chxr parameter. Note that this does not change the scale of the chart elements, only the scale of the axis labels. If you want to make the axis numbers describe the actual data values, set and to the lower and upper values of your data format range, respectively. See Axis Scaling for more information.

You must make an axis visible using the chxt parameter if you want to specify its range.

To specify custom axis values, use the chxl parameter.

http://code.google.com/intl/iw/apis/chart/docs/gallery/bar_charts.html#axis_range

Haim Evgi