How does DataStore work, and how am I using it wrong?

This is a DataStore question, I hate these questions too. I don't quite know hot to throw all the details out there. Anyways, here's the script,

--Regular script in ServerScriptService
local DataStore = game:GetService("DataStoreService"):GetDataStore("wfvj014")

game:GetService("Players").PlayerAdded:connect(function(plr)
    local key = plr.UserId
    local Save = DataStore:GetAsync(key)
    if Save then
        plr.Skill.Value = Save[1]
    else
        DataStore:GetAsync(key,{plr.Skill.Value})
    end
end)

game:GetService("Players").PlayerRemoving:connect(function(plr)
    local key = plr.UserId
    local ValuesToSave = {plr.Skill.Value}
    DataStore:GetAsync(key, ValuesToSave)
end)

There are no errors. I've tested this again and again on servers after publishing the game.* I'm using a table* to save just in case I want to add more values later. The simple fact that I'm using tables might be the problem, I'm unsure.

I made sure the value, plr.Skill.Value, changes before leaving, and when trying to load the data, it seems to reset back to 1. The Skill is not in leaderstats. It's an invisible tracker of the player's skill level.

If you know my problem, please tell me.

Thank you.