About the indicator when the remaining battery charge is low (headset/charging case)

You can check various statuses of the headset by the indicator.

: Turns on in blue / : Turns on in red / -: Turns off

When the remaining battery charge of the headset is low
When the remaining battery charge of the headset is 20% or lower, the indicator (red) lights successively as follows.
- - (repeatedly flashes slowly in red for about 15 seconds)
When the remaining battery charge of the charging case becomes low
When you set the headset into the charging case or remove the headset from the charging case, if the remaining battery charge of the charging case is 30% or lower, the indicator (red) on the charging case lights as follows.
- - (repeatedly flashes slowly in red for about 15 seconds)

https://helpguide.sony.net/