"Graded" means that the weight of the keys differ throughout the keyboard - heavier on the lower keys and lighter on the higher keys. This is how the actual piano feels like, so it is meant to simulate the "real" piano touch. Graded, therefore, only applies to weighted keys.
The pro of this is that you get a realistic piano feel (eg: Yamaha S90). The con is that you will have problem during sequencing. In sequencing different instruments, you want every key to be evenly weighted so that you don't run into trouble of uneven velocities - particularly in sequencing drums.
Back to the CME seller, actually I thought he wasn't too bad. Because the keyboard is not launched yet and their shop is still under renovation, he actually offered to bring the keyboard to my house for me to try. I thought that was quite a nice gesture - I did not take it up because I'm not sure whether I'll be obligated to buy after that...