Aslam mohammad

"aggregate turnover" means the aggregate value of all taxable supplies [excluding the value of inward supplies on which tax is payable by a person on reverse charge basis], exempt supplies, exports of goods or services or both and inter-State supplies of persons having the same Permanent Account Number, to be computed on all India basis but excludes central tax, State tax, Union territory tax, integrated tax and cess;

But to opt for composition scheme ACT provides limitation that the composit dealer cannot sell interstate

No... 

Composition dealer can't make Inter State Supply. So, No way for aggregate turn over calculations with Export or Inter State supply

so what does the word export means here??

where are you reading "word export means", can quote the section

Composition dealer cannot make interstate supplies.