What the grid is, and what it is not
Each square is one week. Each row is one year of age, starting on your birthday, with 52 squares across. The filled squares are weeks you have already lived. The outlined one is this week.
The length of the grid is a setting, not a forecast. It defaults to 80 rows because 80 is a round number. It knows nothing about your health, your family, or where you live, and it would be dishonest to pretend otherwise. Move the slider and the empty part changes; your actual future does not.