Here's a video of the flight, where you can see the charges activate and venting start at about 15:12, the linked time: https://youtu.be/NCYSVmSPM7E?t=663

You can decide how long that is before and after, though I'll note that it may be complicated to determine what's not nominal: Starship has an unconventional staging maneuver that's basically a spin.

I'll also note that "they" didn't send anything; the FTS is autonomous, and will trigger on violation of its conditions, which is probably (1) departure of the instantaneous impact point (where the rocket will hit if all thrust stops now) from a safe ground corridor or (2) indications of disintegration of the vehicle. "The vehicle is doing something weird" is not a condition for flight termination.