If you set the clock once, then the first time it hits zero, the clock will never work again in the game (obviously, the solution is to reset the clock every time you know it hits zero). Depending on how you have everything set up, it might also cause things to instantly respawn because it would keep checking to see if the clock was zero (thus making every 1/10 of a second a tick)

The second timer behaves the same way as the first one, and is completely separate, so in that situation the first timer would stop and the second timer would be set properly - but it would be hidden, and it wouldn't start until you told it to anyway.