Fix Task 2 split counts in meta

benchmark_v2/benchmark_meta.json

@@ -30,15 +30,12 @@
         "mrr_on_positives"
       ],
       "splits": {
-        "train": 43200,
-        "val": 1830,
-        "test": 1578
+        "train": 4202,
+        "val": 1606,
+        "test": 407
       },
-      "positive_counts": {
-        "train": 7200,
-        "val": 305,
-        "test": 263
-      }
+      "corpus_size": 340536,
+      "positive_ratio": "~1:10 negative-to-positive"
     },
     "task3_temporal_generalization": {
       "name": "Temporal Generalization (Unseen CVE Linkage)",