in the case of a person or firm holding appointment as auditor of a number of companies each of which has a paid-up share capital of less than rupees twenty-five lakh, twenty such companies;
in any other case twenty companies, out of which not more than ten shall be companies each of which has a paid-up share capital of rupees twenty-five lakh or more.
In computing the number, the number of companies in respect of which or any part of which any person or firm has been appointed as an auditor, whether singly or in combination with any other person or firm, shall be taken into account.