I was having a similar problem as the OP in that, going with Nikolay's example, the value of the chart's bars would map to the Year's value (being the titles 2007, 2008 from the database), instead of the Value column from the data source. Even though I had mapped the same as:
RadChart1.DataGroupColumn = "Quarter";
RadChart1.PlotArea.XAxis.DataLabelsColumn = "Year";
RadChart1.Legend.Appearance.GroupNameFormat = "#NAME:
I finally got it to map correctly by changing the order of how I was pulling the columns in from the data source (sql query). I had the data columns pulling Value, Quarter, then Year. Once I rearranged the order (sql query) to Year, Quarter, Value (as seen in the example) the numbers magically mapped correctly.