Service tax on salary for contract labour

Hi,

In the Bill of a Contractor who supplies labour to manage the gaming department, he charges Service Fee over and above the Salary of the labour. The Bill Data looks like this;

Salary           XXX

Service Fee   XXX

Total             XXX

ST @ 12.36    XX (On Total Amount)

Kindly advice me if the ST should be charged only on Service fee or on the Total as per Bill.

Thanks in advance :)