Subtracting from a part's position makes it go up?

In a script I'm working on, when an object touches a part with a fire, it should subtract the position of the part by 0.05. However, when testing the part goes up instead of down. What am I doing wrong?

local CheckFire = require(game.ServerScriptService.ModuleScripts.CheckFire)

script.Parent.Touched:Connect(function(part)
	if part:FindFirstChild("Fire") then
		part.FireHealth.Value = part.FireHealth.Value - 0.2
		part.Fire.Size = part.Fire.Size - 0.2
		
		part.Position = part.Position - Vector3.new(0, 0.05, 0) -- This line right here is what I'm most worried about
		part.Size = Vector3.new(part.Size.X - 0.05, part.Size.Y - 0.05, part.Size.Z - 0.05)
	


	
		
		if part.Size.X < 5 then
			part.Size = Vector3.new(5,5,5)
		end
		if part.Fire.Size < 5 then
			part.Fire.Size = 5
		end
		CheckFire.CheckFire(part)

	end
		
end)

Thanks!