Do I enter the whole wear and tear value in my tax return or only the "official" part?

When calculating the wear and tear on my car I take the original cash purchase price and divide that by 5. Do I then enter that value in my tax return (same as all other deductions) and SARS then automatically calculate the "official" part thereof from the kilometers I entered, or do I do the calculation myself and then enter the "official" part in the tax return?

If you are entering the travel allowance section then you would take the total and divide by 5 and they will apportion automatically based on the kilometres you declare.