I agree with Thinkingcap, but I will add that during mixing I try to shoot for a K-20 (sometimes even K-14 if working with pre-processed samples and VSTi’s). By doing this it is almost guaranteed that the levels on my Master Bus will be around or under -3dBFS. Obviously, every mix is different, but that is a trend I’ve noticed since I started mixing using the K-System (included as one of the selectable options in the Cubase meter).