Like what
>>2 said, it's never going to be exactly like the circle, and the integer 4 shown is just Pi rounded up. Think of the concept of 0.999... not equaling 1 because the next number does not have enough value to change the number before, hence it continues to infinite. No matter how much squares you cut, it will never reach the value of the circle, which is why Pi continues forever, as the square cutting process gets closer and closer to it's goal of the real perimeter of the circle, but never actually reaching it.