Developer Product adding random amounts of coins? Why?

So, I have redone how my developer products are functioning. I used this place, "http://www.roblox.com/games/147965737/Developer-Product-Sample" that was on the wiki to help me out. All I did was change the ProductID and then changed the purchase part to give coins instead. I wanted it so that when they buy the product they are awarded 500 'SpiritCoins', though every time I buy it to test it, it gives random amounts each time. It has awarded me 10000, 20000, 30000, 50000, 100000, and 300000. I have NO CLUE why it is random each time I do it when I dont even touch the code each time I buy it. Can anyone help me out please? Thank you!

-- setup local variables
local MarketplaceService = Game:GetService("MarketplaceService")
local ds = game:GetService("DataStoreService"):GetDataStore("PurchaseHistory")
local productId = 26121381

game.Players.PlayerAdded:connect(function()
	print("start")
local DeveloperProducts = game:GetService("MarketplaceService"):GetDeveloperProductsAsync():GetCurrentPage()
for _, DevProductContainer in pairs(DeveloperProducts) do
    for Field, Value in pairs(DevProductContainer) do
        print(Field .. ": " .. Value)
    end
    print(" ")
end
print("end")
end)

-- define function that will be called when purchase finished
MarketplaceService.ProcessReceipt = function(receiptInfo) 

	-- find the player based on the PlayerId in receiptInfo
	for i, player in ipairs(game.Players:GetChildren()) do
		if player.userId == receiptInfo.PlayerId then
			
			
			-- check which product was purchased
			if receiptInfo.ProductId == productId then
				
				-- handle purchase. In this case we are healing the player.
				player.leaderstats.SpiritCoins.Value = player.leaderstats.SpiritCoins.Value + 500
				-- more feedback for the player.
				game.Workspace.DisplayScreen.SurfaceGui.TextBox.Text = player.Name .. " has purchased 500 Spirit Coins."
			end
		end
	end	
	
	-- record the transaction in a Data Store
	local playerProductKey = "p_" .. receiptInfo.PlayerId .. "_p_" .. receiptInfo.PurchaseId
	ds:IncrementAsync(playerProductKey, 1)	
	
	-- tell ROBLOX that we have successfully handled the transaction
	return Enum.ProductPurchaseDecision.PurchaseGranted		
end

I'm not 100% but, to me it looks as if the process Receipt is being called multle times, naturally, to ensure the purchase follows through correctly.

You could try a short denounce:

    -- find the player based on the PlayerId in receiptInfo
    for i, player in ipairs(game.Players:GetChildren()) do
        if player.userId == receiptInfo.PlayerId then


            -- check which product was purchased
            if receiptInfo.ProductId == productId and not player:FindFirstChild("purchaseDebounce") then
               deb =Instance.new("IntValue",player)
              deb.Name = "purchaseDenounce"
             game.Debris:AddItem(deb,0.1)

                -- handle purchase. In this case we are healing the player.
                player.leaderstats.SpiritCoins.Value = player.leaderstats.SpiritCoins.Value + 500
                -- more feedback for the player.
                game.Workspace.DisplayScreen.SurfaceGui.TextBox.Text = player.Name .. " has purchased 500 Spirit Coins."
            end
        end
    end