default long decMemStoreSize(MemStoreSize delta) {
    return incMemStoreSize(-delta.getDataSize(), -delta.getHeapSize(), -delta.getOffHeapSize(),
      -delta.getCellsCount());
  }
Returns The new dataSize ONLY as a convenience
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/MemStoreSizing.java