Should InfluxDb take up more space after retenton period?

I’m hosting InfluxDb v2.6.1 instance on a device that has limited disk space. As I need data from only few days back, I’ve set retention period in each bucket to 7 days (or less). I thought that if I configure it like this, disk space will stop shrinking after 7 days since start of data gathering (data older than 7 days would be deleted, freeing up space for new measurements). Unfortunately, after 13 days my disk space keeps shrinking at the same rate as it did before.

I know it’s InfluxDb, because using this command:

$ du -sk /var/lib/influxdb2

I can see that the directory size is slowly growing.

At the same time, oldest data I can see in Data Explorer comes from 2023-01-05 (which is approx. 7 days ago).

Do I understand retention period correctly? Any ideas comes to your mind what could be taking up space?