AjaxControlToolkit PieChart graphic does not show if only one data value is added

I enter data dynamically from the code behind:

PieChart1.PieChartValues.Add(new AjaxControlToolkit.PieChartValue
{
Category = "1",
Data = count1
});

It supposed to reflect the number of ratings from 1-10 by the use of a switch (I didn't show the entire switch because that would be too cumbersome). So in this case, if one person gives a rating of 1, count1 = 1, and I want the pie chart to reflect that, but instead the control remains blank and only has a 1 all the way at the corner, but the legend is still there.

Is this a bug or am I missing something?