Sorting a stacked chart

Hi all,

I have a grid with 2 fields for ‘group by’. I am then stacking them in a summary chart (see attachment for what this looks like).

I’m unable to figure out how to sort the chart. Would anyone know how to do this? I’d like one set of values to be sorted largest to smallest.

Thanks

Screen Shot 2015-09-07 at 3.38.41 pm.png