Is it normal for the XKAH Pro to beep and turn red when 3 minutes are left?

I bought the XKAH Pro yesterday and tried it for the first time. I was using Custom Mode with a 90-minute session.
At the beginning, I set the temperature to 285°C, and after about 8 minutes I lowered it to 265°C.
When the timer reached 3 minutes remaining, the device started glowing red and beeping. I asked ChatGPT and a few other AIs what this could mean, but I couldn’t find a clear answer.
I also noticed that it smelled slightly burnt, and when I emptied the tobacco afterward, it looked pretty black.
Can someone who has experience with the XKAH Pro tell me if this is normal? Is the tobacco supposed to look like this after a session, or was the temperature too high?