A program has a number of casinos for you to promote. Many programs like that will treat the casinos as the seperate properties they are. That way, if you have a big winner in one casino, it only wipes out your commission in that one casino, and you still get paid for your work from the others.
Bundling is when a loss in one casino wipes out the income from all the casinos. You get nothing and you have promoted 6 or more casinos. That substantially cuts into your income.