The Display panel controls the display of the signal. Usually, oscilloscopes are equipped with a slider to focus the spot of the electronic beam and to adjust the intensity of the spot. In this application, focus and intensity are simulated by selectable pen sizes. The Lines menu is used draw lines on the screen to help you estimating the level and the frequency of the signal. The number of lines to be drawn is controlled by the values for spacing and divisions.
Divisions mean the number of horizontal lines to be drawn.
Spacing is given in Hertz and is intended to estimate the frequency. The Scaling pop-up menu causes the graph to be stretched or shrinked along the time axis. If you prefer white lines on dark background, press the Invert button. Given a sampling rate of 22 kHz, the highest frequency that can be displayed is less than 10 kHz. Whenever you move the cursor over the oscilloscope's screen, you will notice that the cursor's shape changes to a Camera symbol.