DP charges are the depository participant`s charges for the services provided by them, and it would differ from DP to DP.
With Zerodha the charges are below:
IL&FS Charges - Rs.8/-
NSDL Charges - Rs.4.50/-
Total DP Charges are Rs.14/-(12.50+service tax)
When you sell the stock from your Holdings it need to be debit from your Demat account.
So when ever the stock debited from your demat account there would be DP Charges of Rs.14/-.