pert:
It's the exact same output. They want to constrain the value of the variable to be between 0 and 100. Since a is an unsigned type it can never be less than 0 so there's no reason to use constrain in this case. You only need to be sure that the value will not exceed 100, which min() does.
I had read 250
constrain(a, 0, 250);in the first post - but indeed I did not check the type of a