Final answer:
To make the extension column correct, review and rectify any computational errors, adjust the values accordingly, and consult a supervisor if needed.
Step-by-step explanation:
To make the extension column correct, you should review and rectify any computational errors. Double-check your calculations and ensure that the numbers are accurate. Adjust the values in the extension column accordingly to reflect the correct data. If you're unsure, you can consult a supervisor to help you correct the extension column.