Lidless flip chip thermal management clarification document AN-659-1.0.

I am looking at Altera document AN-659-1.0 and it refers to the maximum load of 4g/solder ball for continuous loading on page 12. Does that 4g/solder ball reference the balls on the die or the balls on the chip? If that is the solder balls on the chip, is that also the same value for the solder balls on the die?

Thanks,

mech3dtech