@spiros,
In the code sample provided, two y values were being passed to a dataPoint, whereas a Column chart accepts only single y-value. Also as it’s a Multi-Series chart, passing the dataPoints to the specific dataSeries with label(for displaying string values on axisX) and y-value(for displaying number on axisY) should work fine in your case.
Please take a look at this updated JSFiddle.
__________
Indranil Deo
Team CanvasJS