It means that if you charge the purchase on your Saks CC account, you'll get 3 times 4500 points. By the end of the year, you can get an EGC (electronic gift card) based on your total points earned.
For Neimans, you get double points for all your purchases. Sometimes they have triple points or for certain designer event, you get 6 points per every dollar spent, like the past weekend for Chanel. For every 10,000 points, you can earn $100 EGC.