5 percent rule in sec42

In section 42 for tax reversal,

While calculating amount of tax reversal, govt says assume 5% of common credit is used for personal purpose and reverse that amount.

But in our case, we haven't used any common credit for perosnal use. If we calculate by 5%, the amount is going in lakhs.

Is it compulsory to reverse 5% as used for perosnal... Is there any way to save it or during audit they will check at invoice level and calculate that amount manually(few hundred rupees)....