Problem : ( similar kind of error may be exist in other case possible here I am only discussing about second count down timer case) ;

If the user enter the value greater than 60, suppose 00:00:61 , then after one second delay clock getting formated to 00:01:01, which seems that time stops for one second here .

Solution :
The right countdown happens to be when, when user enters any value in greater than 60 like -> 00:00:65 and then after next one sec delay we gets
00:01:04 .