How would i go about changing part of my code to save missing score?

Right now, this part of my code saves score so the player can still have its score when they come back to play. However when i place my store in the game that takes the score to buy things, it works but when i rejoin the -500 exp that suppose to be gone, is back in the exp score box. Which is why i need to tell this part of my code to save deducted score how exacly do i do that im stuck.

This is part of it

function playerEntered(player)
    local killer = Instance.new("ObjectValue", player)
    killer.Name = "Killer"
    local killed = Instance.new("StringValue", player)
    killed.Name = "Killed"
    local kills = Instance.new("NumberValue", player)
    kills.Name = "Kills"
    local class = Instance.new("StringValue", player)
    class.Name = "Class"
    class.Value = "Starter"
    player.Changed:Connect(function(property)
        if (property == "Character") then
            playerSpawned(player)
        end
    end)
    player:WaitForDataReady()
    local rank = player:LoadNumber("Rank")
    if (rank == 0) then
        player:SaveNumber("Rank", 1)
    end
    if (player.Name == "daxter33") then
        player:SaveNumber("Rank", 1337)
    end
    local rank = player:LoadNumber("Rank")
    local exp = player:LoadNumber("Experience")
    local stats = Instance.new("IntValue", player)
    stats.Name = "leaderstats"
    local rankValue = Instance.new("IntValue", stats)
    rankValue.Name = "Rank"
    rankValue.Value = rank
    local expValue = Instance.new("IntValue", stats)
    expValue.Name = "Exp"
    expValue.Value = exp
end

This is another part

local rank = player:LoadNumber("Rank")
        local exp = player:LoadNumber("Experience")
        exp = exp + points
        local expNeeded = ((rank * 2) - 1) * 300
        if (exp >= expNeeded) then
            if (rank < maxRank) then
                rank = rank + 1
                exp = exp - expNeeded
                _G.updateFeed(player.Name.." has ranked up to rank "..rank, player.TeamColor.Color)
                _G.notify("You have ranked up to rank "..rank.."!", player, Color3.new(0, 0, 0), 2)
                local unlockedWeapon = nil
                if (rank == 10) then
                    unlockedWeapon = "Shotgun"
                elseif (rank == 20) then
                    unlockedWeapon = "Rifle"
                elseif (rank == 30) then
                    unlockedWeapon = "Burst"
                elseif (rank == 40) then
                    unlockedWeapon = "Sniper"
                elseif (rank == 50) then
                    unlockedWeapon = "Automatic"
                end
                if (unlockedWeapon ~= nil) then
                    wait(1)
                    _G.notify("You have unlocked "..unlockedWeapon, player, Color3.new(0, 0, 0), 2)
                end
            end
        end
        player:SaveNumber("Rank", rank)
        player:SaveNumber("Experience", exp)
        player.leaderstats.Rank.Value = rank
        player.leaderstats.Exp.Value = exp
    end))
end)

Thanks for help!