The CYS-S8218 is a nice beefy servo boasting a 40Kg of torque, which is very impressive.
However, this servo does come with one limitation; it has only a 90 degree of rotation output.
When you look inside the servo, there at physical stops at 220 degree and the position potentiometer is also rated to 220 degree, this suggest a lot of reserve capacity within the mechanics, and the manufacture wanting to prevent model builder from overloading the servo by limiting the range to a point it will always have max torque available.