any number in the teens results in 10-1=9
any number in the twenties results in 20-2=18
any number in the thirties results in 30-3=27
any number in the forties results in 40-4=36
ya see the pattern?
so with the same gift appearing in 9, 18, 27, 36, 45, 54, 63, 72 & 81... it's always right.