Thanks yeah i have started doing this, listening out for the low numbers as a priority as then i can get on the brakes in time.
Another problem is that i will strongly disagree with my codriver on the rating of 6 corners quite a lot (normally from the trees or on my roof after what i thought was a quick lift required a heavy brake and downshift) but that's a different discussion!
That happens to me as well occasionally, but it's very rare and happens on lower speed corners, like him saying it's a left 3 and I would call it a "3 tightens" or even a 2. It's a shame that these games don't come with some sort of editing function for pacenotes.
The best suggestion I have is to take the pacenotes with a pinch of salt, only trust a flat left or left 6 if you can actually see the bend and where it leads. A common situation is if he says 6 left over crest and you can't really see where you're going past the crest and are just trusting blindly, lift the throttle slightly or even put your foot ready to touch the brakes, on other words, brace for impact, this way you'll be half ready for anything and will lose at most half a second. He'll never call a 6 where it should be a 3, at most he calls a 6 where it should be a 5 or 6 tightens (from my experience).
Also sometimes he may call a left 6 into left 2 or something, this sort of situation often seems like one turn but it's actually two and you only processed the 6 left and thought the 2 was coming later. Opposite to a 6 long where you can trust it won't tighten bad on you.
Also you should look for dangerous stuff around the place you're putting your car before the turns, sometimes you might just get a wheel on the side of the road or on an uneven surface (stage degradation is a real factor in this game now) and it has the potential to make any 6 into a mess.
But yeah, all in all, this pacenote system is complicated, I just wished I could put on Robert Reid from RBR, his calls felt much simpler to me.