"To start a bulk: add 500 to total calories, to maintain bulk: add 200-300 to total calories depending on weight gained each week"
What that means is when you are first starting your bulk begin by adding 500 calories to your normal caloric intake. As you start gaining weight your caloric intake will of course have to adjust in order to continue gaining, so once you stop gaining that is when you add another 200-300 calories. If you are still not gaining then you add in some more, the trick is not to make huge leaps in caloric intake but to measure and slowly adjust over time.
Like Slayer said its all about finding that equilibrium and then slowly adjusting.