Is this an effective way of creating a random box?

Here is the script:

    local ranGen = Random.new(tick())
    local lSPC = 1
    local rSPC = 2
    local uSPC = 100
    local oSPC = 350

    local function randomBoxChooser()

        local ranNum = ranGen:NextInteger(1, 1000)
        print(ranNum)
        if ranNum >= oSPC then

            return "Ordinary Box"

        elseif ranNum >= uSPC then

            return "Uncommon Box"

        elseif ranNum >= rSPC then      

            return "Rare Box"

        elseif ranNum >= lSPC then

            return "Legendary Box"

        end

    end

I originally had a for loop going up to a thousand and putting in names of the boxes based on probability but that seemed really inefficient to me so I changed it. Just wanted to know if this was the most efficient way. Also later on I Clone the box into workspace at a random CFrame. Now I have read an article on how we should set the parent last and was wondering if that applied to CFrame as well. Here is an example of what I mean:

local box = serverBox:Clone()
box.Parent = game.Workspace
box.CFrame = location

Hope you guys can help. Thanks!