OnScreenTimer is not showing with TimerTrigger

I want to show timer in my custom mission but it is not showing. I checked OnScreenTimer option and connected ExecuteRPNAction block which contains those code:

%((C:Mission:OnScreenTimerValue) flr 60 %)%!02d!.

I got this code from here:
https://docs.flightsimulator.com/html/Additional_Information/Reverse_Polish_Notation.htm

Is this a bug or is there any other methods to show on-screen timer?

It’s a leftover from FSX, not functional. To display things, you would need to create your own html panel.