We know that player characters have significant numbers of points, as do NPC cousins, to say nothing of Elders. And the same is true of Chaosians. But what about lower level characters?
In addition to the ranks from SB, you can make a rough translation from HoC here. In short, two long running campaigns where the mooks have some good numbers. Note that when HoC talks about "+2 against shadow opponents" —that is a shift of two ranks.
IMC, the sentient opposition varies through a number of species and strange environs. Yet the typical opposition is either numbers, such as squads of troops, or sudden unfavorable situations, such as a coup against the government of the shadow you are in. Rarely is the PC's opponent family or Chaosians or a being with some Primal blood.
Those last three types rank at or above the PCs.
In the Eternal City game, Elders are built on 200 to 300 points.
Martin's generation started the campaign with 100 to 200 points.
The PCs started with 100. Virtually no one 'sold down' attributes.
Amber rank '0' is four times the value of mortal shadow competance IMC. There are no shifts, but the scale does start to curve as you push the top end. An attribute of 100 is twelve times the value of mortal competance (or three times better than no points).
Spend nothing on strength at all, and you can figure Gerard is three times stronger than you are.
You can see that mortal quantity quickly become more powerful than Amber attribute quality. So getting back to the original question: IMC mooks typically have zero to negative points. Untrained mortals (75% normal competance) are -140.
Now you know why I more often use 'story value' to figure my plots and opponents than I do points. The points are OK for building PCs, but don't make a lot of sense when you try to figure NPCs. Check out Everway instead where you at least stay in positive numbers.
It may also be clear that PCs are 'heads above' NPCs they encounter. Even two NPCs with some training are really no threat to a zero rank Amber attribute. A more visual example might be that Fiona knows enough martial arts (strength) to take down two ninjas fairly quickly IMC. Three would be a more difficult call, but a good strategy could still give Fiona the win. Four would mean that Fiona would have to make no mistakes, and cause the ninjas to make some, else she would lose.