Cannot get my head around the maths on that one unless I assume they used warp drive.
Having thought about this a bit more, suspect you are more likely to be cancelled on a flight that isn't the first or last of the day. For example, LHR-ABZ has a reasonably frequent service and there is a lot of anecdotal evidence that flights during the day get cancelled and they just throw you on the next one which is soon enough not to have to pay out. First and especially last tend to run OK. Saves on compensation I would suspect, so they make an effort.