For the event costing report, here's how the fields are calculated:
Labor Budget: This corresponds to the field Budget in each event. This gets transferred over from TPP, though I'm not sure how TPP calculates it.
Projected Cost: The sum of each worker's scheduled hours multiplied by each worker's pay rate. Does not account for projected overtime.
Actual Cost: The sum of each worker's actual hours worked multiplied by each worker's pay rate. Does not include overtime.
Bill Total: The sum of each worker's actual hours worked multiplied by the Client Bill rate field for the position worked.