Update README.md

Added a couple of clarifications and size.

README.md

@@ -36,7 +36,7 @@ tags:
 - biomedicine
 pretty_name: PubMed Referenced Question Answering Dataset
 size_categories:
-- 1K<n<10K
+- 10M<n<100M
 ---
 # Dataset description
 
@@ -44,7 +44,7 @@ The PQAref dataset is a dataset for fine-tuning large language models for refere
 
 The dataset contains 3 components:
 - Instruction - question that is supposed to be answered
-- Abstracts - set of 10 relevant abstracts retrieved by IR system from PubMed, containing PubMed id, abstract title and the content of the abstract
-- Answer - expected answer, with references
+- Abstracts - set of 10 relevant abstracts retrieved from PubMed by an IR system. They contain the PubMed id, abstract title and the content of the abstract
+- Answer - expected answer, with references in the form of PubMed IDs.
 
 The dataset was created semi-automatically, utilizing questions available from PubMedQA dataset.