Fractions such as 1/8 or 3/8 would be less than 5/8. (the denominator 8 acts as a sort of unit...1 is less than 5, so 1 eighth is less than 5 eighths)
I didn't use a fraction like 2/8 or 4/8 because these would simplify to 1/4 and 1/2, respectively. (If the top and bottom are divisible by the same number, you divide by that number to simplify...2 and 8 are both divisible by 2, and 4 and 8 by 4)
