Create a pivot widget of RSUM( [Total Quantity] ) over time (rows) and break by (columns) age range.
Scanning down each column, over rows, the numbers only increase. Now change it to a line widget.
The break by defaults from an RSUM within columns in the pivot to an RSUM within rows in the line chart. This is the same as not having an RSUM and doing a stacked area.
Our clients expect the line chart the results from changing the pivot to a line chart, to reflect the same output as the source pivot. As it stands now, they are surprised to see negative curvature in their RSUM, think something is broken, and open a support ticket. The default behavior should be to render Break by Columns instead of Rows.
As an aside, I'm having trouble coming up with, and would be interested in hearing, use cases for charts with break by set to rows.