Update README.md

README.md

@@ -15,4 +15,6 @@ size_categories:
 
 This is a train/test split of 209,571 protein sequences from UniProt of protein sequences with active sites and binding sites labels. 
 All protein sequences (and corresponding binding site labels) are segmented into chunks of 1000 or less. Segmented sequences are indicated 
-by a `_partN` suffix in the Entry column labels. The split is approximately 85/15 before segmentation. 
+by a `_partN` suffix in the Entry column labels. The split is approximately 85/15 before segmentation. The proteins are sorted by family in 
+decreasing order, with families with more protein sequences appearing earlier. Moreover, the split is such that the families in the 
+train/test split are non-overlapping and the `15%` test dataset is composed of the largest families.