There is so much confusion and tripe talked about on this subject. The advice Steinberg give is about input gain, and all they are saying is don't over cook it - because that red light coming on means you went too far. Personally, I really do not like the advice to work much lower for a number of reasons, because it's easy to accidentally record too low, meaning you have to reduce your available dynamic range when you discover there's not enough in the mix. In most cases, you can do this quite transparently, but sometimes (and my bass is a good example) the low recording level brings up with it some of the low level noises between the noise floor and the moderate or quiet playing level.
So I still do what I always did - I play and play as loud as I'm likely to, making sure that is not too much, then I back the knob off a bit giving me some headroom at the top. I have no real interest in how much it is, as long as it sufficient.
Setting -10 to -15 gives you more spare, just in case. If you are likely to go over the peak you have determined best for your session, then having this extra is good. Other people (and I'm one) often end up with this amount of headroom, but I usually notice it afterwards.
Steinberg say don't go over, because if you do it sounds horrible. That's 100% accurate. Headroom is advisable, but not having XdB means very little.
Why is this a big deal? I have no idea?
