A little late, but if this hasn't been answered...
He's saying he doesn't have "D6's" or "'D' sixes;" multiple six-sided dice, in this case used to roll, add the showing total together, and use the sum as a metric to rationalize aspects of one's interactions with the physical, mental, and social world at large.
To fully get this, though... you must Roll Wisdom!
Whether you're in 2nd Ed, 3rd Ed, 3.5/pathfinder, or 5th Ed... well, I'm sure you get it (unless you play 4th Ed; if that's true, I simply can't help you).