why is this health gui glitching out when player zooms out?

local player = script.Parent.Parent.Parent.Parent.Parent
player.Humanoid.Changed:connect(function()
    local redhealth = player.Humanoid.MaxHealth / 4
    if player.Humanoid.Health <= redhealth then
        script.Parent.BackgroundColor3 = Color3.new(255,0,0)
    end
    if player.Humanoid.Health > redhealth then
        local brickcolor = BrickColor.new("Lime green")
        local color = brickcolor.Color
        script.Parent.BackgroundColor3 = color
    end
    script.Parent.Size= UDim2.new(0,(player:WaitForChild("Humanoid").Health / player:WaitForChild("Humanoid").MaxHealth * 200),1,0)
end)

when players health is low the gui glitches the red bar goes bigger then the backgorund. please help. when you zoom out the red bar is not the same size as the background gui so like when i zoom it the red bar's size increases and when i zoom in it decreases. if you do not understand what i am trying to say post a comment then i will show you what i mean.