in notificationworkerlambda/src/main/scala/com/gu/notifications/worker/models/SendingResults.scala [88:94]
def audienceSizeBucket(audienceSize: Option[Int]): String = audienceSize match {
case None => "unknown"
case Some(audience) if audience < 250000 => "S"
case Some(audience) if audience < 1000000 => "M"
case Some(audience) if audience < 2000000 => "L"
case _ => "XL"
}