The game measures a sight from the centre of the screen: x grows to the right and y grows downwards. Screen units are fractions of the screen height, so on a 16:9 screen x runs from -0.889 to 0.889 and y from -0.5 to 0.5. The pink frame shows that edge; anything outside it is off screen. Elements can also be measured in mils, which grow and shrink with the sight's zoom.
The game adds its own range scale, rangefinder and indicators from the other settings. The preview shows the centre lines and the drawing. Text sizes and arc angles are close to the game's but not exact; check a finished sight in a test drive.
Paste a whole sight file or part of one, such as a drawLines block. It replaces the current sight; Undo brings the current one back.