How to set last measure for spline chart ?

I am trying to use a multi axis chart, the column spline from the HTML5 library in JasperStudio. 

So, I have defined a category, a series, and two measures, but I get the following configuration error: For ColumnSpline chart type, the last measure should be used for spline chart. 

WHat HighCharts properties should I set so that the last measure is used for spline chart ? ANd how ?

I have tried:

series.name = name of the last measure
ssriese.type = spline
 

but that does not work at all, I get same error. I would really appreciate if you could help. Thanks !