update readme

README.md

@@ -78,15 +78,15 @@ Prompt2SceneBench can be directly used for:
 Each row in the CSV corresponds to a single prompt instance and includes the following fields:
 
 - `type`: Prompt category — one of `A`, `B`, `C`, or `D`, based on number of objects and complexity.
-- `object1`, `object2`, `object3`, `object4`: Objects involved in the scene (some may be `null` depending on type).
+- `object1`, `object2`, `object3`, `object4`: Objects involved in the scene (some may be `None/NaN/Null` depending on type).
 - `surface`: The surface where the objects are placed (e.g., `desk surface`, `bench`).
 - `scene`: The indoor environment (e.g., `living room`, `study room`).
 - `prompt`: The final structured natural language prompt.
 
 Note: 
-- Type A prompt has only 1 object (object2, object3, object4 fields will be None)
-- Type B prompt has only 2 objects (object3, object4 fields will be None)
-- Type C prompt has only 3 objects (object4 field will be None)
+- Type A prompt has only 1 object (object2, object3, object4 fields will be None/NaN/Null)
+- Type B prompt has only 2 objects (object3, object4 fields will be None/NaN/Null)
+- Type C prompt has only 3 objects (object4 field will be None/NaN/Null)
 - Type D prompt has only 4 objects (all the object fields will have values)
 
 Sample Examples: