Qusetion about removing old backups

I have latest version of UrBackup Server v2.4.13.0
on Ubuntu 20.04.1 LTS
I take backup for both Windows and Linux servers.
I have noticed that I have very old backup although I have configured to take
Maximal number of incremental file backups = 20
Minimal number of incremental file backups = 12
I I understand right. I will take maximum 20 incremental backups and delete the other.
If I don’t understand right, please give me more explanation how I can keep only backup for last twenty days and delete older, because I have 16 TB backup disk and the inode is full now, it is only & TB used. So the only way to save i nodes is to delete files. if you have another suggestions, please inform mew how to do .