How do i make it so when my humanoid Moves a particle emitter size changes?

local Humanoid = script.Parent.Parent:WaitForChild("Humanoid")
local emiiter = script.Parent:WaitForChild("ParticleEmitter")
Humanoid.Running:Connect(function(speed)
	if speed > 0 then
		emiiter.Size = 2
	elseif speed < 1 then
		emiiter.Size = 0.8
		
	end
	
end)

this is the script and when i run it it says invalid argument but i dont excatly know how to fix

ParticleEmitters require a NumberSequence for certain properties like Size.