Ask yourself how important “select paint color for the bathroom” is in the grand scheme of your entire life. It’s an impossible question. As it relates to the bathroom remodel, it’s probably pretty important, but compared to a task from your big work project, even “low” would be overstating it. That’s the trouble with a single global scale: a four-level ranking isn’t granular enough to capture the real nuance of everything on your plate, yet adding more levels just makes it harder to figure out what each task’s ranking should be. Now ask a different question: how important is “select paint color” to the bathroom remodel? That one answers itself. Fairly important, you can’t finish the remodel without it, though perhaps it’s not as blocking as “hire the contractor.” The question got easy the instant you shrank the context. That’s the third job grouping does: it reduces the frame you have to rank within, from “everything” down to “this one project.” Narrowing the scope of the question makes it easier to answer.

So you rate every task’s impact relative to its own project, not against your whole life. “Select paint color”, high, within the project. “Organize the spare-parts drawer”, maybe medium or low, within the garage project, because the garage gets organized fine without it. You’re not comparing the paint color to the spare-parts drawer because they are part of separate projects. Each gets rated in its own small, answerable context, and the weight you gave each project (and domain) handles the cross-project comparison for you later. Grouping supplies the baseline; own impact supplies the nuance. Together they’re the entire ranking story.