Time format for a countdown

[Anonymous_a4260df77c74e08a996a11335d86d3b0 (恶毒瓦斯)]

I want the timer like 00:02:23 to count down to 00:00:00, with your pictures I can get 00:02:23,but it can not count down to 00:00:00.I need your help,I am new UE4 Thank you