Help with wait until?

Hello, I am extremely new to home assist let alone node red lol.

I have begun to create a flow which so far works as intended however I have hit a stumbling block.

I want the intention shown in the screenshot as a wait until node but I dont know how to convert the two.

So the alarm set on my phone in the screenshot if I link that to a button it fires -15 seconds before the alarm goes off which I want in the flow before the next step, I assume its the wait until node but idk?

Tldr how do I make it so the toggle off then goes onto wait until 15 seconds before my phones next alarm before going onto triggering the next event.

I hoped it was a case of simply connecting the two but the time node doesnt acept inputs only outputs.