text: Title: [layoutlmv3]: Issue with label format? Inference yields boundary boxes that are too short.
  Body: Hi, 
  
  I am working on object detection with layoutlmv3.
  
  I am using the publaynet fine tuned model and have a training set with about 600 documents. 
  
  The issue that I am facing is that the predicted boundary boxes are only kind of correct. In most of the documents the predicted boundary are "too short". Meaning that the lower y coordinate is usually too small.
  
  As an example I have attached you an example from my evaluation dataset. It is the case in almost every single inference picture. Thus, I am trying to get some ideas to troubleshoot.
  
  I double checked that the drawn boundary boxes in the inference is correctly done.
  
  ![ak_state_of_alaska_2020_p144](https://user-images.githubusercontent.com/40527435/202876949-c6e41860-ee7d-4b2f-b34b-c2d7ef7cdd4a.jpeg)
  
  ![inference](https://user-images.githubusercontent.com/40527435/202876954-87cab2cc-5f26-4142-a661-d9e7abfb9931.jpeg)
  
  Any ideas would be greatly appreciated.
  
  