Reporting over contracts - need help

Hi there. I am running 7.11.20 and want to use the reporting engine to create a pie chart showing the summary value of contracts ending by month, before a certain date.
I can get the detail report to give me this, but the pie chart only shows a segment per contract (coloured coded into months) and the hover over shows the value of the individual contract to 4 decimal places.

Any idea how to get the report just to show one pie slice per month, with the total amount of contract value for the month?
pie chart.PNG|594x500

Can you share the Screenshot for the Conditions and Fields of Report?

Here yo go…

And the conditions (just the one!)