There are two datasets on the chart - first representing revenue and the other representing profit. The user can visually drag and adjust both these values to simulate the figures. Since revenue cannot be less than 0 in any case, we do not allow the revenue columns to go beyond 0 value by setting allowNegativeDrag property to 0. Also, we've assumed that the profit in fourth quarter cannot be negative. So, we've set its individual allowNegativeDrag property to 0 too. The rest of profit columns can however go into negative zone.