In this video I discuss how to make a 24 hour clock and the issue when using Tick vs Seconds. I also talk a little about modulus. This tutorial uses modulus or % in division. If you are not familiar with modulus I have tried to explain it below.
"7 % 2" would evaluate to 1, because 7 divided by 2 has a quotient of 3 and a remainder of 1, while "9 % 3" would evaluate to 0, because the division of 9 by 3 has a quotient of 3 and a remainder of 0
So in the code we use ClockSeconds%60 to see if we need to add 1 to the seconds variable. ClockSeconds%60 = 0 means we have a multiple of 60 (no remainder) so we add to seconds if ClockSeconds%60 is not = 0 then that means we don't have a number divisible by 60 (we have a remainder).