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

https://wiki-aero.win/index.php/How_Do_I_Calculate_Average_Rate_of_Change_Between_Two_Times%3F

Learn how a running total differs from a rate of change with parcel deliveries: packages accumulated by day versus packages per hour during a shift. See how units and time windows change what a chart tells you.