Why is a 4Float Parameter not a 4 Float?

Thanks you for the fast answere.
Maybe my english is to bad, but i do not understand whats the issue.
So the Parameter is a 3 float? is there a way to make it a 4 float? (without doing it like me) like I plug the RGBA value in to the (Clamp/Shift/Multiply (V4)) pin?
or is is how i did the correct way?