A running total tells you how many parcels have arrived so far, while a rate of...
https://wiki-site.win/index.php/How_Do_I_Write_a_Sentence_That_Makes_the_Interval_Obvious_in_a_Rate%3F
A running total tells you how many parcels have arrived so far, while a rate of change shows how many arrive per hour. This article explains how units and time windows help you tell those numbers apart and use them with confidence.