How do I do this devproduct where the amount of damage done is doubled?

	local events = game.ReplicatedStorage.Events
	local MarketplaceService = game:GetService("MarketplaceService")
	local data = game:GetService("DataStoreService")
	local productId = 134836943
	timer = data:GetDataStore("PurchaseHistory1")

	events.punchEvent.OnServerEvent:connect(function()
	MarketplaceService.ProcessReceipt = function(receiptinfo)
		local player = game.Players:GetPlayerByUserId(receiptinfo.PlayerId)
		if receiptinfo.ProductId == productId then
			local currentTime = os.time()
			local lastTime = timer:GetAsync(player.UserId)
		if lastTime then
			local timePass = currentTime - lastTime
		if timePass <= 15 then
game.StarterPack.Fight.Main.Fighting.Damage.Damageamt.Value =
 game.StarterPack.Fight.Main.Fighting.
	Damage.Damageamt.Value*4
else
	game.StarterPack.Fight.Main.Fighting.Damage.Damageamt.Value = 10
				end
			end
		end
	end
end)