If one of the companies whose stocks you hold announces a buyback, you may participate in the same if you wish to, through your broker (Zerodha).
If you are eligible for the buyback, you would receive a Tender form to your registered email id from the Company’s RTA. You can apply for the buyback on Console (on Zerodha). More info here.
Once the shares are tendered in the buyback, you would need to pass on the details of the shares tendered to firstname.lastname@example.org, so that the same is updated in your smallcase as well.