Production
Crew man-hours and production rates.
What these production calculators are for
One tool turns a completed quantity and the hours it took into a rate. The other turns a remaining quantity and a known per-person rate into crew hours and man-hours. They are inverses of the same relationship: quantity = rate × time × (optional headcount).
Which tool to open
Production rate: you already placed or excavated a quantity and know the hours. Crew man-hours: you have quantity still to do and a per-person rate from a similar crew. Keep the quantity unit consistent (cy in, cy/hour out). Neither tool adds weather, mobilization, or access; those stay on the schedule.