Based on the nature of corporate action, adjustments will be done in the base price, option strike values, and the market lot of the contracts, as per the adjustment factor. 

Adjustments for corporate actions aim to ensure that the value of market participants’ positions on the cum and ex-dates remains as consistent as possible. This helps maintain the relative status of positions, such as in-the-money, at-the-money, and out-of-money.

In certain instances, adjustments may lead to the alteration of the contract’s expiration date, prompting the contract to be forcibly closed before the initial expiry date. Subsequently, adjusted contracts will be introduced for trading in its place.

You can refer to this exchange link to find out the exact methodology used by NSE to calculate the effect of different corporate actions and the adjustment factors used for the same.