Video and audio timer

I would like to set up a timer of let’s say a 1 /2 hour
where a pop up would occur to both parties screens 15 seconds before the 1/2 hour time limit disconnect
and that both parties would need to click within that 15 second timeframe to continue chats video and audio

You can add a time limit

But I think you need to edit the code for it to add that 15 second reset window

thank you