Why Does this FE script give me a nil value when it is played?

I have this FE script that goes nil when it is played. This is the error 20:42:48.509 - Players.powerdud.PlayerGui.LocalScript:2: attempt to index local 'XP' (a nil value) I don't understand why this doesn't work. If someone could help me it would be much appreciated.This is my code

Server script

game.Players.PlayerAdded:connect(function(Player) 
	local Data = Instance.new("IntValue",Player) 
	Data.Name = "Data" 
	local XP = Instance.new("IntValue",Data) 
	XP.Name = "XP" 
	XP.Value = 0
    local Level = Instance.new("IntValue",Data) 
	Level.Name = "Level"
	Level.Value = 1 
	local Tries = Instance.new("IntValue",Data)
	Tries.Value = 10
	Tries.Name = "Tries"
	local ExCap = Instance.new("IntValue",Data)
	ExCap.Value = 500
	ExCap.Name = "ExCap"
	XP.Changed:connect(function() XPChange(Player,XP,Level,ExCap) end)
end)



function XPChange(Player, XP, Level, ExCap)
	game.Workspace.RemoteEvent:FireClient(Player,ExCap,Level,XP)
    end 

Basically XP is changed it will fire a Event called FireClient

Local script

game.Workspace.RemoteEvent.OnClientEvent:Connect(function(Player,ExCap,Level,XP)
	    if XP.Value >= ExCap.Value then
        if Level.Value < 100 then
            Level.Value = Level.Value + 1;
            XP.Value = XP.Value-ExCap.Value;
            ExCap.Value = ExCap.Value * 2;
        end
    end
    if Level.Value == 100 and XP.Value ~= 0 then
        XP.Value = 0;
end
end)

When XP rises more than ExCap, XP will subtract from ExCap