Owl: Your e-scooter battery shows 88% when you leave campus at 3:10. At 3:40 it shows 61%. Something clearly moved — but "it went down" is too vague for calculus.
Did it drop steadily, or mostly on that last hill? Over forty minutes, or only while the motor was under load? Change has a size, a direction, and a window of input — usually time.
On the board I've also sketched a café's average wait: 4 minutes at opening, 11 minutes at the lunch rush an hour later. Same idea: a quantity, an independent clock, a net jump.
Before we name rates or slopes, I want your honest first pass. What questions would you ask so "what changed?" becomes precise instead of hand-wavy?