Options Value At Expiry

When an option expires ITM, what will be its value? Let’s Nifty closed at 17316 on an expiry day, the 17350PE for that expiry will have what value after expiration?
My understanding is that it should have an intrinsic value of 17350 - 17316 = 34/-. However, I see that it expired at 18.

Could someone please explain what am i missing here?

The final closing price of Nifty is 17331.8, the final closing price is the weighted average price of the last 30 minutes of trading. This can differ from the LTP you see at 3:30 PM. You can learn more about this here: How to determine closing price in F&O? - #2 by Karthik

So the 17350 PE will expire with an intrinsic value of Rs. 18.2 (17331.8 - 17350).

Thanks. It makes sense.

However, for one who is looking at charts and trading this will be a surprise(like me today). 34 and 18 have a huge difference.