In India, we follow the T+1 settlement cycle. Simply put, if you buy a stock on Tuesday, it gets delivered to you in your demat account by Wednesday. The amusing part is that even before the delivery gets made, you are allowed to sell it.
With BTST (Buy Today Sell Tomorrow), stock is sold even before it makes it to your demat account.
Let’s say that you have bought 50 shares of Tata Motors on a Monday and sold them the next day. According to the settlement cycle, the shares you bought will be transferred to your demat account on Tues. On the very same Wednesday, 50 shares of Tata Motors will be earmarked for (Sell) delivery based on the sale that happened on Tuesday. These shares will then be debited from your account and settled on Thursday, i.e., the T+2 day.