@Override
    public double[] getSnapshots() {
      double[] result;
      int startIdx = getStartIdx();
      int endIdx = getEndIdx(startIdx);
      int resultSize = (endIdx - startIdx) + 1;

      if (filter != FILTER_NONE && resultSize > 1) {
        long[] timestamps = null;
        if (filter == FILTER_PERSEC) {
          timestamps = resource.getAllRawTimeStamps();
        }
        result = new double[resultSize - 1];
        int tsIdx = resource.getFirstTimeStampIdx() + startIdx;
        double[] values = series.getValuesEx(descriptor.getTypeCode(), startIdx, resultSize);
        for (int i = 0; i < result.length; i++) {
          double valueDelta = values[i + 1] - values[i];
          if (filter == FILTER_PERSEC) {
            double timeDelta = (timestamps[tsIdx + i + 1] - timestamps[tsIdx + i]); // millis
            valueDelta /= (timeDelta / 1000); // per second
          }
          result[i] = valueDelta;
        }
      } else {
        result = series.getValuesEx(descriptor.getTypeCode(), startIdx, resultSize);
      }
      calcStats(result);
      return result;
    }
Provides the value series related to a single statistics.
geode-core/src/main/java/org/apache/geode/internal/statistics/StatArchiveReader.java