When you reach the maximum amount of points in your current level range you will not receive more paw and fur points but instead receive a boss point that will allow you to choose any boss within or below your level range. You may only do a boss below your level range once, this is intended so you can get the achievements.
If you are level 130+ and have maximum points, once you complete a task you can use this boss point to do all lower tier bosses without having to spend the point. This only works with the boss point from a task on level 130+.
For example, if you are level 130, have 100 points, and finish the Hydra task. You may use this point to kill all bosses from the lower tier once, then spend it to kill the Ghastly Dragon boss. Then, in the long run. Whenever you complete a task you can spend that point to do whichever boss you prefer in the level 130+ range.