I put Set text to "" on purpose. If you think about it, with that line, the text displayed should remain blank. Instead, the Layout name is displayed on each tick, as if Trigger Once did not exist.
I'll put another example, to see if you understand better the fact that TriggerOnce is not working.
In this case Variable2 should only increment when you press 1 or 2 with the keyboard. However the variable keeps incrementing, completely ignoring the TriggerOnce condition.