Another way to think of this is that "box" might be considered somewhere close to where the first high quality print can be made and the limit of the "extra" category would be where the last high quality print can be made.
There are real reasons to consider these alternate placements.
Exposing for the last HQ print point might eliminate the need for carrying an ND filter.
Exposing extra somewhere between the limits could also give you consistently longer print times, making complicated burn and dodge work more manageable.
An example of the use of truly over is a high-key technique I used in studio, the subject is lit to provide proper placement for easy printing at the desired level. The background is then lit to truly overexpose well beyond where detail could be recovered. Creates a stunning white that leaves the subject beautifully isolated.