These are the 8 points of off balance.  If you are in a stance for example, and your right foot is on position 2 and your left foot is on position 6, then the off balance points to that stance are at positions 8 and 4.  You can figure out off balance points by taking a stance and then drawing a line connecting both feet.  Take a perpendicular line off of the center line that you had drawn between both feet and you will see 2 off balance points in that stance.  One forward and one backwards.  Look at another example, if your opponent is in a neutral stance with their right foot at position 3 and their left foot at position 7, you can pretty easily see the off balance points there.  The straight line between the feet is already drawn, it would be between points 3 and 7.  The perpendicular line is drawn off of them towards position 1 and position 5.  What this means is that in that stance, you could take your opponent and pull them towards position 1 easily and they would fall.  If there feet remained stable, you could push them back towards position 5 and they would fall with little to no effort on your part.  Balance breaking is the key to controlling an opponent and moving them with minimum effort.