Contribution to epf

Below is the extract from EPF Act as on their site. Can anyone tell me the funda of 10% & 12%.

6. Contributions and matters which may be provided for in Schemes. – The contribution which shall be paid by the employer to the Fund shall be ten percent. Of the basic wages, dearness allowance and retaining allowance, if any, for the time being payable to each of the employees whether employed by him directly or by or through a contractor, and the employee‟s contribution shall be equal to the contribution payable by the employer in respect of him and may, if any employee so desires, be an amount exceeding ten percent of his basic wages, dearness allowance and retaining allowance if any, subject to the condition that the employer shall not be under an obligation to pay any contribution over and above his contribution payable under this section:

Provided that in its application to any establishment or class of establishments which the Central Government, after making such inquiry as it deems fit, may, by notification in the Official Gazette specify, this section shall be subject to the modification that for the words “ten percent”, at both the places where they occur, the words “12 percent” shall be substituted: