Briyani rice is not plain rice bro. It is cooked in ghee or oil with spices, which is exactly why it smells and tastes so good, and exactly why a plate of the rice alone is around 450 calories, well above a normal scoop of white rice. The chicken gives you solid protein, around 38g for the plate, but the rich rice is the real calorie story.
Mutton briyani (kambing) is often quoted slightly lower per plate because the pieces are smaller, even though mutton is fattier per gram. Either way you are in the 700 to 900 range for a typical restaurant plate, higher if they are generous with the ghee.