I’m assuming it’s referring to two regular dice? (2 dice with numbers 1-6 labeled)
The divisors of 8 are 1,2,4, and 8
I’m interpreting as rolling the number on the die not the sum of the dice
So it’s 3/6 numbers on the die or 1/2 and there are two dice to rolling a divisor of 8 on both dice is 1/2 x 1/2 or 1/4