[-Azrael666-]

There's a few ways.

1. At the beginning, set the countdown trigger to a high time, like 3 hours. People can see how long they've played by how much time has passed.

2. Make a set of triggers which say how long it's been after so much time passes. Such as, a trigger that when Elapsed Time is 300 seconds, it displays the message "5 minutes have passed." Just make one for ten minutes, fifteen minutes, etc.

3. When the game starts, have a trigger set the countdown timer to 1 second, then pause the countdown timer. Now, have another trigger add 1 second to the countdown timer for every second that passes (just put a Wait between the Modify Countdown Timer and Preserve Trigger).

Any of those methods work for keeping track of time that's passed.