Pricing per person for the booking engine has to be added on the Amenitiz side, for Booking.com side it has to be added on Booking. If the pricing per person is not set properly before the connection with the channel manager, the OTA will receive the wrong price.
To do so, you can connect yourself to your Booking.com account.
Once you are inside, go to > Rates & Availability and to > Calendar:
You have an overview of your different rooms as well as the rates that are set for every different room.
You can see from here the pricing per person already set on your Booking account, and modify it by clicking on "edit" or "set up".
If you don't have access to the button "edit", or if the occupancy type is not the good one (a discount instead of an increase for example), you can delete and re-create your rate plan to make this feature appear.