Logging during backup or howto disable the "skipping msg with key" msg?

Hi!

We are using CouchBase Server 3.X,
In one bucket we have alot of different instances of the same product running, every instance has it’s own unique prefix:
DE1::…
US2::…

To get a consistent backup, we shutdown one instance and only backup the values of this instance.
We are using the the following command:
cbbackup CB_HOST CB_BACKUP_DIR -u CB_ADMIN_NAME -p CB_ADMIN_PASS -b CB_BUCKET_NAME -k CB_WORLD_KEY

The CB_WORLD_KEY could be for example US2. This works fine … but we get a lot of this logging messages:
2015-10-13 07:25:59,582: w1 skipping msg with key: TSO::02::190672

The bucket contains around 200 000 000 ojects and we only backup ~ 20 000 000 at a time … so we will get 180 000 000 log messages!

Now the question: how can we avoid this log messages? We found no option for this.

Thanks alot!