Simple query

CENVAT is nothing but the setoff of Excise duty or service tax if any paid on Inputs , capital goods and service tax.

For eg. you are having a mfg. unit which was regstd under excise act.
Now you bought inout say rs. 100 on which you have paid Basic excise duty of Rs.8.24. So total value is 108.24.

Now you have processed this Input and one new product got manufacured and you sold this for rs.200 + 16.48 excise duty on that.

As you have paid 8.24 at the time of purchase , you are eligible for cenvat credit of such amount and hence you have to balance of 8.24 in cash. (16.28 on sale - 8.24 on purchase = 8.24 payable in cash)