Exchange uses weighted average price of last 30 minutes of trading to determine the final closing price/settlement price for the day, this can vary from LTP (Last Traded Price).
On Kite, around the next day morning. The settlement price will be updated instead of LTP once we receive the BHAVCOPY (daily report with OHLC data, traded value, qty, OI etc.) from NSE.
Due to this, the LTP value for F&O contracts changes to the settlement price instead of the last traded price.
This support article explains it in detail.
The day you take the position, brokerage and charges for that leg Long/Short will be charged at the EOD.
Now if you haven’t squared-off your position before expiry, then if the position expires OTM, it’ll expire worthless and no charges will be applicable.
If the position expires ITM, brokerage will be applicable and if it is Long Option position, exchange too charges STT at 0.125% on the intrinsic value.
You can check out this post for more details: What happens if I don't square off my positions in options? - #2 by ShubhS9