How would I add a minute timer for my game countdown?

I am currently using a loop to countdown the amount of time left in my game. The current amount of time a round in my game lasts for is 600 seconds or 10 mins. How would I make it countdown from 10:00 instead of 600?

This script is very short because it is SO easy;

also set; "ResetOnSpawn" enabled in the current screengui you are editing

local timer = script.Parent
local minutes = 2
local seconds = 19
 
repeat
    if seconds <= 0 then
        minutes = minutes - 1
        seconds = 59
    else
        seconds = seconds - 1
    end
    if seconds <= 9  then
        timer.Text = tostring(minutes)..":0"..tostring(seconds)
    else
        timer.Text = tostring(minutes)..":"..tostring(seconds)
    end
    wait(1)
until minutes <= 0 and seconds <= 0

#Explanation

If the seconds is smaller than 0 then the minutes is equal to itself - 1 else the seconds will subtract by themselves

and you know the rest