The top report always shows both Income and Expenses by month for the length of your date range.
Both the bar and pie charts follow the same Filters that the reports follow. In fact, when you run a Description/Payee Report, when you click over to the Chart Tab, it will be displaying a Description Pie chart.
So when you are creating reports, in the background the charts are also being created. Clicking on the Charts Tab at any time will reflect your current filters, thus displaying only the information that is included in the report. A future version will allow you to embed charts within your reports for reference.