As the scanner rotates in a counter clockwise direction, it is going from 0 degrees, increasing to 360 degrees.
This is correct. As the scanner rotates counter clockwise, the angle increases from 0 to 360, before resetting upon the next rotation.
Therefore on an XY chart...
The mapping of angle to cartesian coordinates is accomplished via the standard:
x = radius * cos(angle in radians)
y = radius * sin(angle in radians)
Here, x and y are simply conventions of a right handed coordinate system. In the case of the visualizer, the starting camera angle (top down view) shows the x axis extending to the right and the y axis extending upward. In the visualizer, the zero degree mark is the positive x-axis, chosen because it is a direct result of the formulas for intuitive conventional mapping from polar to cartesian coordinates (shown above). This means that, in the visualizer, the positive x-axis will align with data from that has a recorded angle of 0 degrees.
For reference, the actual zero angle mark is the LED/thin groove on the front of the device. Try pointing the led at an obvious visual landmark, and then rotate the device slowly back and forth while viewing the data in the visualizer. You can see data change and track the landmark. Note that a sensor reading with an angle of 0 degrees will always be drawn along the positive x-axis... while a sensor reading with an angle of 90 degrees will always be drawn along the positive y-axis.
Summary: the angle associated with a reading is dictated by the orientation of the device's head relative to the physical zero mark (led/thin groove). You can map that to whatever coordinate system you like.
Hope that helps.