code: public static final int getMaxUpdatableSerializationBytes(final int lgConfigK,
        final TgtHllType tgtHllType) {
      final int arrBytes;
      if (tgtHllType == TgtHllType.HLL_4) {
        final int auxBytes = 4 << LG_AUX_ARR_INTS[lgConfigK];
        arrBytes =  AbstractHllArray.hll4ArrBytes(lgConfigK) + auxBytes;
      }
      else if (tgtHllType == TgtHllType.HLL_6) {
        arrBytes = AbstractHllArray.hll6ArrBytes(lgConfigK);
      }
      else { //HLL_8
        arrBytes = AbstractHllArray.hll8ArrBytes(lgConfigK);
      }
      return HLL_BYTE_ARR_START + arrBytes;
    }
docs: Returns the maximum size in bytes that this sketch can grow to given lgConfigK.
  However, for the HLL_4 sketch type, this value can be exceeded in extremely rare cases.
  If exceeded, it will be larger by only a few percent.
  
  @param lgConfigK The Log2 of K for the target HLL sketch. This value must be
  between 4 and 21 inclusively.
  @param tgtHllType the desired Hll type
  @return the maximum size in bytes that this sketch can grow to.