Yes you are right - to be able to exploit most of the chart area you should use the MinValue and MaxValue properties of the axisY and/or axisX. Don't forget to turn off the AutoRange property of the axis and set the desired step. For more information refer to this link - http://www.telerik.com/help/silverlight/radchart-features-axes-overview.html
I hope it gets you started properly.
the Telerik team
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