What do I need to be doing differently? (TweenSize)

I'm trying to figure out how to tween the size of my gui button so it smoothly encompasses the size of the screen, but tween seems to only shrink it.. do I need to be using a different method, or what?

Button = script.Parent

local click = false
Button.MouseButton1Click:connect(function()
    if not click then
        Button.Text = ""
        Button:TweenSize(UDim2.new(0,0,0,0), "Out", "Quint", 0.3, "false")
        click = true
    end
end)

I've played around with the values, and nothing seems to enlarge it.