Script is not counting down from 24 hours, why is this?

I'm making a script where it counts down from 24 hours. How do I fix this script to count down properly?

local function CountDown()
    if script.Parent.Visible == true then
        local RawTime = workspace.ShopKeeper.Timer.Value
        local Hours = math.floor(RawTime/3600)
        RawTime = RawTime - (Hours * 3600)
        local Minutes = math.floor(RawTime/60)
        local Seconds = RawTime - (Minutes * 60)
        if string.len(tostring(Minutes)) == 1 then
            Minutes = "0"..Minutes
        end
        if string.len(tostring(Seconds)) == 1 then
            Seconds = "0"..Seconds
        end
        local TimeString = "Inventory refreshes in: ".. Hours..":"..Minutes..":"..Seconds
        script.Parent.Time.Remaining.Text = TimeString
    end
end

CountDown()
workspace.ShopKeeper.Timer.Changed:connect(CountDown)