num_samples in _info should be at split level, not dataset

_info.json

@@ -3606,8 +3606,8 @@
                 1200,
                 1200,
                 1141
-            ]
+            ],
+            "num_samples": 2159432
         }
-    },
-    "num_samples": 2159432
+    }
 }