The sweep angle represents the amount of the scale that is used to display ticks. By default there is space between the first and the last value of the scale.
If you want to specify the sweep angle use the SweepAngle property. For example a value of 360 will make the scale to form a complete circle and the first and the last value will overlap each other. A value of 180 will uake the scale use only half of the circle to display the values.