Code:
  ; First letter only (first hint and also if $len < 4 and also for numbers)
  if ($2 == 1 || $len($1) < 4 || $1 isnum) { return $left($1,1) $+ $right($replace($1, [ %replace ] ,a,*,e,*,i,*,o,*,u,*,y,*),-1) }


Change that part.

Again, that 4 is what you need to change if you want it to only give the first letter for words greater than 3.

As it is now, you have this:
Answer: Fun
Hint1-3: F**

Answer: Test
Hint1: T***
Hint2-3: Tes*

Answer: Three
Hint1: T****
Hint2: Thr**
Hint3: Three

If you want, you can increase 4 to 5 and then all 4 letter words will only have a 1 character hint for all hints. Increase to 6 and all 5 letter words will only get 1 character hints. Just decide what you want.