How do I use number values in my math.random() statement?

Hello, I need help, I need to use math.random() in my script and to make it easier to customize, I made the lowest and highest number a number value, but it doesnt work, is there any reason why?

return function()
    while true do
        wait(script.Parent.Parent.WaitDelay.Value)
        local lowest = script.Parent.Parent.LowestSpeed.Value
        local highest = script.Parent.Parent.HighestSpeed.Value
local speed = math.random(lowest,highest)
script.Parent.CylindricalConstraint.AngularVelocity = speed
    end
end

Thanks.