Update README.md

README.md

@@ -34,11 +34,11 @@ train-eval-index:
       name: Rouge
 ---
 
-This is a copy of the [Multi-News](https://huggingface.co/datasets/multi_news) dataset, with its input source documents replaced by a __sparse__ retriever. The retrieval pipeline used:
+This is a copy of the [Multi-News](https://huggingface.co/datasets/multi_news) dataset, except the input source documents of its `test` split have been replaced by a __sparse__ retriever. The retrieval pipeline used:
 
 - __query__: The `summary` field of each example
-- __corpus__: The union of all documents in the `train`, `validation` and `test` sets
-- __retriever__: BM25 via [PyTerrier](https://pyterrier.readthedocs.io/en/latest/) with default settings _except_ for no stemming was applied.
+- __corpus__: The union of all documents in the `train`, `validation` and `test` splits
+- __retriever__: BM25 via [PyTerrier](https://pyterrier.readthedocs.io/en/latest/) with default settings. The number of documents retrieved, `k`, is set as the original number of input documents for each example.
 
 Retrieval results on the `test` set: