Unknown source of notifications after fresh install

I have a fresh install of the Android app. And did not set up any notifications so far. Also, I did not configure anything regarding mobile device notifications in my Home Assistant installation. Nevertheless, I receive regular (several times per hour) notifications with just a message containing a number in range -2 til 3. I have no clue where those are coming from. Is this a known issue or is there anything configured as example I am missing?

notifications will only show up by the app if you set them up in a notification. Try checking logbook.

I haven’t set up any. New app version did solve the issue. Thanks.