def _get_min_max_blk_len(fill_info):
    """Helper method to get minimum/maximum fill lengths used."""
    blk0, blk1, blkm = fill_info[1][4], fill_info[1][5], fill_info[1][8]
    if blkm < 0:
        blkm = blk0
    return min(blk0, blk1, blkm), max(blk0, blk1, blkm)