It's not that specific. It lets you keep track of low medium and high demand and supply, and only in stations you visit and only if you decide to record them. This allows you to make generalisations such as "take this commodity from a high supply place to a medium demand place and you'll make more profit than if you take it to a place with no demand. This is completely unlike tools like Slopey's (nothing against those tools, I just prefer to play it like this) which give you access to information you wouldn't normally have and will give you specific amounts of profit available. It's basically the same sort of thing many of us were recording with paper and pencil, without having our desks covered in scraps of paper.