Total Chargeback for the previous month KPI gives the total cost that was billed to the selected project in the previous month.
The Project Chargeback information is available in details on the Reporting page. You can also call or2report command to get total or resource-specific report. For example, the followoing command will result into a detailed resource report by your project (you can see data for either current or previous months):
or2report -p project -r region -m month -y year -t resource -e