How to use variables set conditions in trigger functions for player NEXT button

I would like to set a trigger for the player NEXT button.

There is a option available to set "slide.elapsed.time" and the variable only allows a number. What does this number mean?

I want the NEXT button in the player to be active when a certain number of seconds have elapsed. How do I do this and format triggers for player navigation buttons?

Currently, I create my own Next button and set the triggers as I like. To avoid having the users navigate on the slide instead of on the player tools only, is there a way to program the player buttons?

Is there a written tutorial that describes what all the available conditions and variables mean? Thank you.