With 263 marks under the BCM (Backward Class Muslim) category, your chances of securing a seat in a government Unani college in Tamil Nadu depend on several factors, such as the overall cutoff trends, the number of seats available, and the competition in your specific category.

Typically, the cutoff marks for admission to Unani medical colleges can vary each year based on the difficulty level of the NEET exam, the number of applicants, and the reservation policies in place.

To get the most accurate and up-to-date information, it’s best to check the previous year’s cutoff marks for the BCM category in Tamil Nadu’s government Unani colleges. This will give you a better idea of your chances of admission.

If you still want more precise information, I recommend visiting the official counseling website for Tamil Nadu medical admissions or directly consulting with experts or counselors who specialize in medical admissions.