If you hold existing quarterly or half-yearly contracts which are not equivalent to the new lot size then, you have the following options:

Option 1: Adjust your position to align with the updated market lot size on or before the specified transition date. For example, if you have an existing position in Nifty of one lot i.e., 25 quantities, and the new Nifty lot size is 75 quantities then you have to add another 50 quantities to your existing position.

Option 2: Square off your existing odd lot position before the new lot size is applied. For example, if you have an existing position in Nifty of one lot i.e., 25 quantities, and the new Nifty lot size is 75 quantities then you have to Square off your existing position.