Dr P: If you are calculating the savings for a specific phone call, knowing the number of seconds (10,000 and 20,000 seconds in your example), then there isn’t any average savings as you know the precise amount of billable seconds in whatever interval billing you are comparing. Am I not following?
Also, with pure 6-second interval billing the average savings (compared to 60-second) was 27.0 even. Yet in the examples you are demonstrating in your last comment for 6-second with a 30-second minimum, you are calculating average savings of 27.0032 and 27.0018 seconds. Which of course is a greater savings than you calculated for pure 6-second billing. Obviously in no case should 30/6 (scenario 2) have greater savings than 6/6 (scenario 1).