All the rice. Apparently it is indeed for "sushi"... Amazon link (also posted below):
https://www.amazon.com/Camp-Chef-Sushezi-Roller-Kit/dp/B001P8J1GU/ref=lp_2600075011_1_1?srs=2600075011&ie=UTF8&qid=1479139834&sr=8-1
Even in the images on Amazon, they use about 20x as much rice as filling... and the rolls appear to be ~ 4-5 cm in diameter.