code: @VisibleForTesting static long calculateTargetReps(long reps, long nanos, long targetNanos,
        double gaussian) {
      double targetReps = (((double) reps) / nanos) * targetNanos;
      return Math.max(1L, Math.round((gaussian * (targetReps / 5)) + targetReps));
    }
docs: Returns a random number of reps based on a normal distribution around the estimated number of
  reps for the timing interval. The distribution used has a standard deviation of one fifth of
  the estimated number of reps.