For 'OR' case, we have either a is divisible by 6 or b is by 8. Total #states = 48 as in 'AND' case.
Only final states will be more. We will count final states like (0,x) and (x, 0) where x E [0,5] for 'a' and [0,7] for 'b'.
For 'a' we have 6 such final states, for 'b' we have 8.
Total 6 + 8 - 1 = 13 final states as we have counted state (0,0) twice.