I ran into this same problem the other day! These are the only articles I found on it:
My guess is that "float literal" just means that you have to type an actual number in for that argument - it will not accept other calculated fields or parameters, even if they are formatted as a float. Again, that's just a guess based on what I'm reading and what I have experienced.
That explanation doesn't seem right though.
This is because after I change my parameter input directly as a float, e.g., 0.50 instead of 50, the calculation works perfectly. Maybe it does not accept a formula at the 2nd argument (x/100)?
Huh. Yeah I don't know. But I guess you found a solution to your problem then, right?
It's still more intuitive for the end user to enter an integer (50 rather than 0.50) in the text filter though.
Let's see if any other zen masters can resolve this. >__<