The KendoUI charts proportions are incorrect for the supplied data when the given group field starts with a number.
If you look at: http://dojo.telerik.com/IquMa (or the attached File1) you will see when you hover over the bars the percentages shown don't actually match the proportion of the chart.
The same data but with a different group field name (not starting with a number) you end up with it working as per:
http://dojo.telerik.com/IPexa (or the attached File2), however the colours are wrong.
The above represents a simplified scenario but highlights the issue.