How Would One Set a Range for a Raycast?

Here's my code:

local rayOrigin = humrp.Position;
local rayDirection = direction.p;
		
local rayCast = Ray.new(rayOrigin, (rayDirection-rayOrigin).unit*20);
local part = workspace:FindPartOnRay(rayCast, character, false, true);

Where "rayOrigin" is the player's HumanoidRootPart Position and the rayDirection is "mouse.Hit.p"

I assumed the "unit*20" would set the range of the raycast to 20 but I guess I was very wrong haha. The raycast fires a beam that can go as far as it would like. How would I set the range of the ray to 30 studs?

Any help is greatly appreciated! Thanks!