Graylog notification "Elasticsearch nodes disk usage above low watermark"

In System/Overview of my freshly installed Graylog version 6.1.1 (there’s nothing configured, no data so far), I have notification “Elasticsearch nodes disk usage above low watermark”.

I don’t understand why I get this warning because my installation is based on Data Node and services like ‘elasticsearch’ or ‘opensearch’ I don’t have installed and don’t see them running.

I’m using latest version of Debian 12 Bookworm with Graylog version 6.1.1

Can someone explain how to get a rid of this warning, does it mean any problem, are there any known solutions to this?

Thanks everyone for suggestions and have great day everyone.

This might help