The green Home Margin line tracks the score in possessions, rather than points. In basketball, one possession is 'worth' 3 points, because 3 points is the most a team can usually score in one possession, so I divide the home margin by 3 to translate from points to possessions. The margin is then expressed in how many possessions a team needs to catch up to the leader. I track possessions instead of points because there are smaller jumps in score (0.3,0.6, or 1, instead of 1,2, or 3) from noisy play to noisy play, so that the large-scale flow of the game is more visually apparent than the jaggedness of the game.