Delta 4 takes   1.3333 rolls on average to be depleted
Delta 6 takes   3.3333 rolls on average to be depleted
Delta 8 takes   6.0000 rolls on average to be depleted
Delta 10 takes  9.3333 rolls on average to be depleted
Delta 12 takes 13.3333 rolls on average to be depleted
Delta 20 takes 20.0000 rolls on average to be depleted