def parse(cls, fptr, offset, length):
        """Parse number list box.

        Parameters
        ----------
        fptr : file
            Open file object.
        offset : int
            Start position of box in bytes.
        length : int
            Length of the box in bytes.

        Returns
        -------
        LabelBox
            Instance of the current number list box.
        """
        num_bytes = offset + length - fptr.tell()
        raw_data = fptr.read(num_bytes)
        num_associations = int(len(raw_data) / 4)
        lst = struct.unpack('>' + 'I' * num_associations, raw_data)
        return cls(lst, length=length, offset=offset)