This is a special section consisting of either: 6' of mesh pre-attached to three poles and ground sleeves with caps for all poles or 3' of mesh pre-attached to two poles and ground sleeves with caps for both poles. (2.5' or 5' for 5' tall)
The loose pole is also a convenience. Last sections in fences are rarely exactly 6' or 5' or 10'. With the loose pole all you need to do is drill your final hole where you need it, put the pole in place, and then pull the mesh tight around the pole and replace the backing to hold it. This will give you a perfect end section every time.