docs: public static int getUpdatableStorageBytes(final int k, final long n) {
      if (n == 0) { return 8; }
      final int metaPre = DoublesSketch.MAX_PRELONGS + 2; //plus min, max
      final int totLevels = Util.computeNumLevelsNeeded(k, n);
      if (n <= k) {
        final int ceil = Math.max(ceilingPowerOf2((int)n), DoublesSketch.MIN_K * 2);
        return (metaPre + ceil) << 3;
      }
      return (metaPre + ((2 + totLevels) * k)) << 3;
    }