You may consider notional wages, i.e., the salary which he would have earned had he been employed throughout the month. Since that notional wage exceeds Rs. 21,000, you can exclude him from ESI. This principle applies to overtime wages as well. Overtime wages are excluded from deciding the coverage of an employee but are considered for the contribution of a covered employee. Therefore, if due to overtime the salary of an employee exceeds Rs. 21,000, he should not be excluded.