Learn how a running total differs from a rate of change with parcel counts....

https://activecalculus.org/author/Running-Totals-Rates-of-Change

Learn how a running total differs from a rate of change with parcel counts. “120 parcels by noon” is a total, while “15 parcels per hour” is a rate. The article shows how units and time windows help you read a work chart and compare what happened.