Nice and original, but the writing of the fractions was a bit off.
maybe have a selector you can adjust the whole numbers, numerator, and denominator with +/- buttons?
Could also go with more levels.
Level 1 could be for multiples of 1/2, level 2 for multiples of 1/3, level 3 for 1/4s, etc.

And after level 99: the boss round converts to decimals from X/100.