The OI percentage difference for a particular strike price between 2 subsequent trading days is first calculated. Suppose Union Bank of India has 3 different strike prices: Rs.162, Rs.165 and Rs.168.

In the above example Rs.165 strike price has the highest call option OI as well as recorded the highest percentage increase in OI over the previous day.

The same exercise done for 2 days separated by 5 trading days results in the highest 1W OI change call option strike. The maximum increase in percentage change is sought out and this is the strike with the highest call OI change.