Ace firmware update mode

[Guest tsr2]

My mother has a Galaxy Ace and it sometimes comes up with a warning about a custom OS potentially damaging the phone.

 

I think she is accidentally holding the volume key while powering it up and starting it in firmware update mode. I have demonstrated to her what the problem is and hopefully it won't happen again.

 

She says, if she is not quick to cancel it with the volume down button, it says it is downloading and she can't turn it off except by removing the battery. Is there any other way to turn it off at that point?

 

As she hasn't downloaded any firmware, is it safe to assume that she can't do any damage to the phone?