Grouping in pie chart isn't accurate

While I was verifying ZEPPELIN-1889, I tried grouping with pie chart, when I tried grouped data, I think, it's only displaying information from the first group

• Use bank data from example spark job that comes with Zeppelin.
• Wrote an sql query: select * from bank limit 100;
• In the visualization settings, select pie chart
• Set- key: marital, groups: education, value: avg(balance)

Results displayed in graph:

• Divorced: 61% 487
• Married: 50% 399

This is statistically correct, I guess, because, there is one more result: 'single: -11% -91', which cannot be displayed on a pie chart

But the chart only displays data from people who completed only primary education, where as it should display results from people with other educational qualifications