Why has Nadal's ATP points total remain unchanged despite the fact that he won Monte Carlo and Rome AMS?

the system is very complicated. all points remain with a player for 12 months so the points nadal got for winning rome and monte carlo last year expired at the end of the tournaments and he had to win to defend those points or his point total may have dropped if he did not win. (may have because the rankings only take into account a certain number of tournaments (15 or 20?) at a time and ignore the rest of the tournaments you play.)