Generally, this depends on the model and capacity of the Philips air fryer you purchase. The Philips TurboStar Air Fryer XXL, for instance, has a capacity of 3 lbs. The serving may also depend on the exact recipe you are trying to make. The Philips XXL has enough space for 1.4kg of chicken and 6 medium potatoes at the same time.
You can fill your Philips Airfryer up to the "MAX" indicator on the basket. But it is important to note that this max volume would depend on the kind of food you're preparing. Be sure not to overcrowd the appliance. Even though air fryers are known for even cooking, you may not get desired results if you overcrowd the unit.