[SOLVED]How to make a script that runs a math.random , and doesn't run when they rejoin?

You shouldn't be using DataPersistance. Simply use Datastores to save your data, and if the Value isn't there to load, it randomizes one. Example:

local DataStore = game:GetService("DataStoreService"):GetDataStore("PlayerStat") -- This is like a folder
game.Players.PlayerAdded:connect(function(plr) --once they join
    local Data = ("Data" .. plr.UserId) 
    local DataTable = DataStore:GetAsync(Data) or {math.randomseed(1,5),0,0,0} --and the other data that needs to be saved
    local Data = Instance.new('IntValue', plr) -- this isn't shown to other players, not leaderstats
    Data.Name = 'Data'

    local random = Instance.new('IntValue', Data)
    random.Name = 'RandomMove'
    random.Value = DataTable[1] or math.random(1,5)
    --other saves
end)

This is just a bad example I quickly made, it probably even has mistakes. You'd still need to add the end of the script that saves it once they leave, but I'm not going to take that much time making you an actual script. This is just to help you understand how Datastores look like, so please research them and you'll find that easy.