Unable a project's actual hours onto a resource estimate report chart.

Hi Samantha - actual hours for a resource are not captured on a Resource Estimate object type. Only budgeted and scheduled (which are planned).

Since you can reference the project, you can technically add the project's total actual hours, but that number would appear on each line item. BUT, if you Average, Min, or Max in the "Summarize this column by" option, that might help. I don't know how your report is laid out, but if you want total for the project (and not by role), that might help.