@Override
    public long heapSize() {
      return ClassSize.align(FIXED_OVERHEAD)
        // array overhead
        + (rlength == 0 ? ClassSize.sizeOfByteArray(rlength) : rlength);
    }
These cells are used in reseeks/seeks to improve the read performance. They are not real cells
that are returned back to the clients
hbase-common/src/main/java/org/apache/hadoop/hbase/PrivateCellUtil.java