Cst on esciseable goods

Dear All,

I need help in one of the case, in normal case CST is calculated on exciseable amount, for eg. if sales is 30 lakhs and 12% excise duty is calculated on 30 lakhs, so considering 2% and 1% Edu. cess and high edu cess total excisable amount comes to rs.33,70,800/=, and on this amount CST 2% is calculated

My question is in which situation CST is calculated on base amount i.e rs.30 lakhs? is any thing like deemed export?

Regards.