Hi Dado and welcome to the community!
DadoTC wrote:as expecting to see on disk jus the last .vib file... I see 3 .vib instead, why ?
Incremental files .vib contain only changes of VMs images and can't be used for restore without the rest data from the full backup file .vbk and all earlier .vibs.
Veeam B&R cannot delete previous files because .vib itself would be unusable, so when the next full .vbk will be created according to your settings, the old backup chain
will be erased by the retention rule.
Please, review existing thread about backup chains in details
DadoTC wrote:because it see that today I already have the full backup in place?
DadoTC wrote:To go to the point... how can I now clean up the disk so I have just one full backup and one incremental backup ?
You can use Forever Forward Incremental
backup method and set up retention to keep 2 restore points.