Every month a lot of traders in India loose unnecessary money as STT to the govt..
When an option expires in the money STT is 0.125% of the contract and not 0.017% on premium, if you sell it in the market...
So for eg, if the option is trading at say Rs 20, if you sell it in the market, the STT you pay would be around 0.17 Rs(0.017% of Rs 1000) Now the same option, if you held it to expiry and closes in the money, the STT now is 0.125% of the contract, which would be 0.125% of 275000(5500x50) around Rs 340 or almost 7 points difference...
In your case, you feel it should have closed at 17 because the nifty closing was 5483 and it closed at 13.. Ideally it should have closed at Rs 10( if you considered the 7 Rs STT that you have to pay) ...