You will need:
2 Lifecycles
1 Relay
1 Repeater
1 Tag Zone
1 Counter
1 Property
First, wire a 2 separate lifecycle to a repeater. That way when the game starts and when a player joins late the relay triggers on behalf of all players.
Next, wire the relay to a repeater, so when the relay is triggered the repeater will start.
The repeater has to run the task every second. Stop it when receiving on a channel but don’t put a channel name down.
After that, Wire the repeater to a counter, when the task is run, increment the counter. Now wire a tag zone to the repeater. The player gets tagged , stops the repeater. Now place down a property that’s named secs lived. Now in the counter make it update the property secs lived. Put that property in the leaderboard and you’re done!