local weapons = game:GetService("ReplicatedStorage").Weapons

for _, folder in ipairs(weapons:GetChildren()) do
    if folder:IsA("Folder") then
        local DoubleJump = folder:FindFirstChild("DoubleJump")
        if not DoubleJump then
            DoubleJump = Instance.new("NumberValue")
            DoubleJump.Name = "DoubleJump"
            DoubleJump.Value = 0.2 -- change to wtv u want
            DoubleJump.Parent = folder
        end
    end
end