for (; real_size > 0; --real_size) {
    if (hist_freq_[real_size - 1] != 0) break;
  }

  hist_stats.set_lower_bound(lower_bound_);
  hist_stats.set_bin_width(bin_width_);
  hist_stats.mutable_hist_freq()->Assign(hist_freq_.begin(),
                                         hist_freq_.begin() + real_size);

  CalibrationStatistics statistics;
  statistics.mutable_histogram_statistics()->CopyFrom(hist_stats);