STCG in share trading

Flat 15% tax over any STCG left after adjusting it from Basic exemption limit.

1. According to sec 111A, STCG on sale of shares on which STT is paid will be taxed @ 15%. 
2. The unexhausted basic exemption limit if any will be exhausted on the above gains and the balance amount will be subject to tax @ 15%. 
3. In the above case, the balance unexhausted amount will be reduced from STCG and the balance STCG (if any) will be taxed @ 15%. 
Please correct me if the above solution has an alternative view.