Your unique DP Id is a 16 digit alpha-numeric or just numeric number. For the CDSL depository account, all 16 digits are numbers.
For NDSL depository account, the first 2 digits are alpha and the next 14 digits are numbers.
Now, the first 8 digits represent your Demat service provider called DP. It will be the same for all the clients of that broker.
Next 8 digits represent your individual Demat account number with your Demat service provider which is also called beneficiary ID. It will be unique to you.