How to convert this?

So you want to make a clock. First we will look at some methods that will help us with this. % mod or modulus is an operator that returns the remainder of number1 divided by nuber2 so ...

10%3 = 1 

this is because 10 goes into 3 perfectly 3 times then has 1 left over so this returns 1. SO how do we implement this well we simply use this to find the number of seconds left in the minute. so our code now would look something like this

for i = 60, 0, -1 do
    Time = "there is " .. tostring(math.floor(i / 60)) .. ":" .. tostring(i % 60) .. "Seconds left"
    wait(1)
end

So that code did 2 things first we found the minute by dividing the number of seconds by 60 and rounding that number down. Don't confuse this with the % operator because they are not the same thing. The first operation returns how many times i can evenly be divided by 60 while the second operation returns how far i is past the interval of 60.

hope this helped