This article explains running totals and rates of change with parcel...

https://violetmetric.com/s/x6qd3oH1dcwQZYPfr5M0i

This article explains running totals and rates of change with parcel deliveries. Compare 120 parcels by noon with 15 parcels per hour, then see how the time window changes what the numbers mean and why keeping units attached helps you read a chart.