You can't..
The dotted line shows the view from coordinate 0,0 (top-left) to x,y (bottom-right) where x = project-width and y = project-height..
You could always use the viewortleft(), viewporttop() etcetera to spawn based on viewport..
Or if you want to do it your way, scrolling to a sprite, viewportleft would be sprite.x - 0.5* (your project width) as long as you don't use fullscreen-scaling, for that might change the coordinates of your viewport-edges..