A running total tells you how much has piled up, while a rate of change shows...

https://rapid-wiki.win/index.php/Why_Is_the_Derivative_Zero_Between_Jumps_on_a_Step_Graph%3F

A running total tells you how much has piled up, while a rate of change shows how fast it’s growing. With parcel counts or rainfall, the article explains why units matter and how a daily rate differs from a weekly total over the same span.