relative change formula seems wrong

[stvno]

While testing the application I noticed that lower average speeds have higher percentage changes when compared against the reference speeds. This is counter intuitive: a lower average speed should have a lower percentage change. I checked the code and noticed that the formula to calculate the percentage change seems weird: https://github.com/opentraffic/analyst-ui/blob/0a9861d40600a2d15656bbb424a54091050ecb1c/src/app/processing.js#L33 The way I would assume would be (average-reference)/reference *100 as per https://en.wikipedia.org/wiki/Relative_change_and_difference
Any particular reason we are not using the simple formula?