Find the Median of a list<int> in Dart

I have a list of integers which contains times in milliseconds (ex. 1433, 834, 1020..). I need to calculate the Median. I developed the following code but the Median I get is completely wrong compared to the one I calculate in Excel. Any ideas? is there any Dart/flutter library I could use for statistics?

  /// Calculate median
  static int calculateMedian(TimeRecordNotifier timeRecordNotifier) {
    List<int> mList = List();
    timeRecordNotifier.timeRecords.forEach((element) {
      mList.add(element.partialTime);
    });

    //clone list
    List<int> clonedList = List();
    clonedList.addAll(mList);

    int median;
    //sort list
    clonedList.sort((a, b) => a.compareTo(b));

    if (clonedList.length == 1)
      median = mList[clonedList.length - 1];
    else if (clonedList.length % 2 == 1)
      median = mList[(((clonedList.length) / 2) - 1).round()];
    else {
      int lower = mList[((clonedList.length ~/ 2) - 1)];
      int upper = mList[(clonedList.length ~/ 2)];
      median = ((lower + upper) / 2.0).round();
    }

    return median;
  }

On the following dataset the expected median value is 901,5, however this algorithm gives me 461

Solution

I refactored the code into this using NumDart implementation and now it works. thanks @MartinM for you comment!

/// Calculate median
  static int calculateMedian(TimeRecordNotifier timeRecordNotifier) {
    List<int> mList = List();
    timeRecordNotifier.timeRecords.forEach((element) {
      mList.add(element.partialTime);
    });

    //clone list
    List<int> clonedList = List();
    clonedList.addAll(mList);

    //sort list
    clonedList.sort((a, b) => a.compareTo(b));

    int median;

    int middle = clonedList.length ~/ 2;
    if (clonedList.length % 2 == 1) {
      median = clonedList[middle];
    } else {
      median = ((clonedList[middle - 1] + clonedList[middle]) / 2.0).round();
    }

    return median;
  }