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The annual charges are AMC charges and this is DP. Every brokerage charges similarly for demat.
DP charges are only the selling side and not buying side, basically DP charge is when you sell shares from the demat account.
If you sell 3 different scrips like you have mentioned, even if they are many times in a day, you will be charged DP charge thrice at the end of day. 3 * Rs 12.5. Do note that DP charge is not applicable for intraday trading.