The maximum course size that you can set up with SwiftPaws for home is limited by the motor's capabilities. We say "around 200-300 feet" because that's typically the size course you'll be able to set up.
Under ideal conditions you might be able to set up a course that is quite a bit a larger. Under less than ideal conditions that put tension or drag on the system (uneven terrain, tall grass etc.) you might have to make a smaller course.
See: Ideal Conditions