This graph is based on a simple idea from numerology but it attempts to show you something rather grandiose: a sort of forecast for the whole life.
Specifically, it predicts the level of life energy that will power different periods of the person's life. This life energy is somewhat similar to Ying and Yang in Chinese tradition. When the graph goes up, towards levels 8 and 9, life energy becomes very Yang and the person spends a significant amount of time in the outside world, doing something that is visible and recognised by everyone.
This kind of graph was often used to try and predict when the person will marry: supposedly, when the graph is high.
And vice versa, when the graph is low, the person tends, or maybe is forced, to have a solitary, secluded existence. This is the time of invisible, inner work that can be related to raising children, writing a book, an intense study or sometimes an illness.