Fc is a fancy way of expressing the net force.
At the bottom, there is weight force (Fg) downwards and tension (Ft) upwards.
Hence Fc = Ft - Fg.
Thus, Ft = Fc + Fg.
At the top, the net force (Fc) is Fg + Ft as both are in the same direction.
Hence Fc = Fg + Ft.
Thus, Ft = Fc - Fg.