How could i fix/do this?

For one it does not count down properly, and two, how could i make it so it works correctly? Is their anything wrong with this? Its a round countdown, i just want it more fancy and advanced.

local Second = 60
local Minute = 05
local Minutes = "0"
local Seconds = "0"

while true do
    wait(1) 
    if tonumber(Second) < 60 then
    Second = Second - 1 
    if tonumber(Second) == 00 then
    Minute = Minute - 1 
    end
    end
    if tonumber(Minute) < 10 then
        Minutes = "0"..Minute
    else
        Minutes = Minute
    end
    if tonumber(Second) < 10 then
        Seconds = "0"..Second
    else
        Seconds = Second
    end
    script.Parent.Value = "Time left: "..Minutes..":"..Seconds
end