See how a running total differs from a rate of change with daily parcels: 120...

https://romeo-wiki.win/index.php/What_Does_%E2%80%9CIntegrable_Rate%E2%80%9D_Mean_in_Simple_Terms%3F

See how a running total differs from a rate of change with daily parcels: 120 delivered by Friday is not the same as 24 parcels per day over five days