When we say ₹20 brokerage that does not mean that you are going to pay only extra ₹20 to complete your transaction. You have below given charges when you do one transaction in exchange-
Total Brokerage & Taxes = Brokerage + Transaction Charges + SEBI Turnover Charges + STT Charges + Stamp Duty + GST on Brokerage and Transaction Charges
SEBI Turnover Charges
So when you come to conclude your transaction, you are charges – brokerage, Transaction charges, STT, SEBI Charges, Stamp Duty and GST.