Chart Web Part - how to have it use totals instead of each instance?

I am trying to use the chart web part with the following list:

The list includes production hours.  It has a column for year, month, worker name, their department, and, among other things, their total hours.

I am trying to have a pie chart, or some kind of chart, that shows a department's total hours for each month.  The problem is, no matter what I'm doing, it's referencing every record, so the legend is huge, the pie chart has tons of entries, etc.

What am I doing wrong?  I don't want to see each individual entry, I want to see the department's totals.  So, if 20 employees in department cheese did 500 total hours of work in month january, the pie chart would show department cheese with 500 total hours of work for that month, but instead it's showing 20 entries for that.  

Thank you.