Problem with sync audio and timer.

I have a really simple project, A music start with a simple timer (timer += time.deltatime), and when the timer hits 24, this trigger an event, Ok, on my computer works as it's intended, but on another computer the event start in another time, like 28 or 30, I know about the processor timing and we have to use time.deltatime to avoid "frame timing", but both music and timer start together and the timer use time.deltatime, so, what I'm doing wrong?