Shares will be sold at Strike Price, ie. 2100. You must have not accounted for charges arising through physical settlement. For physical settlement, STT is applicable at 0.1% on the physically settled value, if you calculate, this tallies exactly to Rs. 1050.
Yes, 0.25% in case you’re giving or taking delivery of shares and 0.1% in case the positions are netted-off. You can check this post for more information.