Offset is not a valid member of UDim2?

 local Raritytimes = {
    ["Common"] = 70,
    ["Uncommon"] = 25,
    ["Rare"] = 5
}
local RarityColors  = {
    ["Blue"] = 170, 255, 255,
    ["Green"] = 0, 255, 0,
    ["Dark Green"] = 0, 170, 0
    }

local CrateInude = false
local function opencrate(Chance)

    if CrateInude == false then
        CrateInude = true
        local items = {}
        local frametimes = math.random(30,32)
        local rewardbutton
        for i,v in pairs(game.ReplicatedStorage.Items:GetChildren()) do
            local rarnumber = Raritytimes[v.Rarity.Value] or 1
            local mathmatical = math.max(Raritytimes["Common"]and Raritytimes["Uncommon"] and Raritytimes["Rare"] + Chance)
            for i = 1,mathmatical do
                table.insert(items,v)
            end
        end

        math.randomseed(tick())    

        for i = 1,frametimes+5 do
            local item = items[math.random(#items)]
            local newsapme = script.Parent.CommonCaseOpening.SampleItem:Clone()
            newsapme.Visible =true
            newsapme.Parent = script.Parent.CommonCaseOpening.Inner
            newsapme.Icon.Image = item.Image.Value
            newsapme.ItemName.Text = item.Name
            newsapme.Position = UDim2.new(0,100*(i-1),0,0)
            if i == frametimes then
                rewardbutton = newsapme
            end
        end
        for num = 1,(rewardbutton.Position.X.Offset - (255+math.random(-40,40)))/15 do
   for i,v in pairs(script.Parent.CommonCaseOpening.Inner:GetChildren()) do
    v.Position = UDim2.new(0,v.Position.X.Offset-15,0,0)
    if v.Position.X.Offset <= -150 then
     v:Destroy()
    end
   end
   wait(0.01 * 1.05 ^ (num-105)/2)
   script.Tick:Play()
  end
 end
end

opencrate(0)

This should work! Position.X.Offset not Position.Offset

EDIT: I NOTICED MY ANSWER WASN'T POSTED. AND NOW IT IS SOLVED - SO I PUBLISHED IT NOW