Derivative function: Is there a relations between collector interval, $interval in grafana and time parameter of derivative function?

After having read all docs and examples i still don’t understand the time value parameter we set in (non)derivative function: It is set by default on 1 second in almost every dashboard panels (grafana) but why?

How to calculate it?

if i have a collector (telegraf) configured for 2 second interval collection, a grafana dashboard $interval variable set on 1 or 10 second, what should be the derivative time value?