Card: describe how samples were chosen

README.md

@@ -47,7 +47,7 @@ results on Haystack remain reproducible. The authors' code is at
 
 ## Samples
 
-Four random test images (fixed seed) with the boxes of every object that takes part in an annotated relation. Green lines are positive relations; red lines are negatives an annotator explicitly rejected for the same pair.
+Four images drawn at random (fixed seed) from the 61 that have at least two positive relations, two to eight negatives and at most five objects in relations, with the boxes of every object that takes part in an annotated relation. Green lines are positive relations; red lines are negatives an annotator explicitly rejected for the same pair.
 
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 <img src="https://huggingface.co/datasets/maelic/Haystack-coco-format/resolve/main/assets/sample_1.jpg" width="49%">