Thank you for reaching out to Microsoft Q&A forum!
Based on your query, I would suggest labeling the two columns separately as two different tables to ensure that the custom built model reads the two tables in the correct order. You can label the left column as "Table 1" and the right column as "Table 2". This will help the model understand that there are two separate tables and that they need to be read in a specific order.
Additionally, you can also add more training data to your dataset that includes this specific format of tables. This will help the model learn and recognize this format better. By adding more training data, the model will have more examples to learn from and will be better equipped to handle similar formats in the future.
I hope this helps! Thank you.