APC Back-UPS Pro, 1500VA mute function

[MathewSI]

Hi! I am trying to understand the user guide of the mentioned UPS. From page 6 of the user guide:

"The Mute function will not activate unless the Back-UPS is operating on battery power."

What does this mean?

1. That you have to unplug UPS from ac in order to activate mute function? Does not make sense.

2. That alarms are muted only when on battery power? All of them?

3. Only operating on battery power alarm can be muted? Makes sense but can not be it, because they would have put this simple logical statement in the manual.

4.?

Thank you for your reply

Mathew