Showing 2 stacked barcharts in 1 widget

I’m having trouble combining two stacked bar charts in one widget on a dashboard.

I want to show some financial information. First, I created a chart showing budget costs, per month (x-axis) per ledger, say marketing, service, development, etc (stacked y-axis). Next, I created a similar chart but this time show the actual costs. So far no problems.

Now I want to combine both charts on my dashboard in one widget where budget and actual are shown side by side. I know how to add multiple series to one widget. But budget and actual are summed in the dashboard chart. So the marketing budget and marketing actual for October 2017 are summed in the stacked bar chart.

How can I show budget and actual next to each other?
Could my problem have to do with a warning saying: “‘Date’ is an unaggregated field: if it has more than one value at a point on the x-axis, the values will be summed.”