The situation you described, where your 12th grade marks were entered correctly but the total was incorrect due to an online hub mistake, is a common issue that can cause concern for students preparing for entrance exams like the BCECE. However, there are several steps you can take to address this problem and minimize its potential impact on your application.

1. Contact the Online Hub Immediately: The first and most crucial step is to contact the online hub responsible for entering your marks. Explain the situation clearly and provide evidence of the correct marks. They may be able to rectify the error promptly.

2. Obtain a Corrected Marksheet: If the online hub can correct the error, request a revised marksheet with the accurate total. This corrected document will be essential for your BCECE application.

3. Document the Issue: Even if the error is resolved, it's important to document the entire process. Keep copies of correspondence with the online hub and any supporting documents. This documentation can be helpful if any issues arise later.

4. Contact the BCECE Authority: If the online hub is unable to resolve the issue promptly, contact the BCECE authorities directly. Explain the situation and provide evidence of the correct marks. They may have specific procedures for addressing such discrepancies.

5. Provide Additional Evidence: In addition to the corrected marksheet, you may be asked to provide additional evidence of your 12th grade performance. This could include copies of your class tests, assignments, or other relevant documents.

6. Follow Up Regularly: Keep in touch with both the online hub and the BCECE authorities to ensure that the issue is being addressed in a timely manner. Follow up regularly to check on the progress and provide any additional information that may be required.

While this situation can be stressful, it's important to remain calm and proactive. By taking the necessary steps to address the error and provide the required documentation, you can increase your chances of a successful BCECE application.