I've marked up the cavity photo, which may help with my explanation.
If you used a 'normal' pot for the tone (as you get with a PBG kit) and wired it in the manner of the SG, then because the opposite end of the pot track is being used as opposed to the normal end, then the pot would work in reverse, with 10 being dullest and 0 being brightest. The tone pots therefore are reverse-acting types (sometimes used on left-handed guitars), where the pot operates in the opposite way to a 'standard' pot. Or at least it should. However a quick search reveals that the 'D' in front of the pot resistance value normally indicates a slight variant on a log/audio taper pot (though there are no guarantees if the pot is old), so it may be that the tone pot does operate in reverse!