Why is this adding more than it should?

This keeps adding more than 10 like its suppose to... I've had this problem for many days and I can't find out why..

server script :

local DataStore = game:GetService("DataStoreService"):GetDataStore("PurchaseHistory")
local MarketService = game:GetService("MarketplaceService")
local productId = 23429504

function CompletePurchase(player)
    local stats = player:WaitForChild("leaderstats")
    local cash  = stats:WaitForChild("Cash")
local debounce = true    
cash.Value  = cash.Value + 10
end

MarketService.ProcessReceipt = function(receiptInfo) 
    for i, player in ipairs(game.Players:GetChildren()) do
        if player.userId == receiptInfo.PlayerId then
            local ID,PROD = receiptInfo.PlayerID, receiptInfo.PurchaseId 

            if receiptInfo.ProductId == productId then
                CompletePurchase(player)
            end
        end
    end 

    local playerProductKey = "plr_" .. ID .. "_pur_" .. PROD
    DataStore:IncrementAsync(playerProductKey, 1) 

    return Enum.ProductPurchaseDecision.PurchaseGranted     
end

just incase you need this script : server script

local player = game.Players.LocalPlayer
local credits = game.StarterGui.MainGuis.Shop.Credits
game.Players.PlayerAdded:connect(function(player)
    local stats = Instance.new("Folder",player)
    stats.Name = 'leaderstats'
    local cash = Instance.new("IntValue",stats)
    cash.Name = "Cash"
    cash.Value = 10
    credits.Text = "Cash: "..player.leaderstats.Cash.Value..'$'
end)

promptpurchase script : local script

local buy = script.Parent
local productId = 23429504
enable=true
buy.MouseButton1Click:connect(function()
if enable==true then 
enable=false game:GetService("MarketplaceService"):PromptProductPurchase(game.Players.LocalPlayer, productId)
enable=true
end
end)