BackupCopyJob - Simple Retention Policy

[serverbu]

There occured a question on the transformation process performed on BackupCopyJob backup chain with simple retention policy when the maximum number of restore points is reached.
The documentaion states

The backup chain transformation is performed in the following way:
1.Veeam Backup & Replication re-builds the full backup file to include changes of the incremental backup following the full backup. More specifically, it injects data blocks from the first incremental backup in the chain into the full backup. This way, a full backup ‘moves’ one step forward in the backup chain.

How exactly is injects to be understood?

The fullbackupfile has a size between 0.9 and 1.0 TB the daily increments a size between 80 to 120 GB. The Job is set to keep 14 restore points.
So pure backup would need 1 TB one time plus 120GB thirteen times making it sum up to around 2.6 TB.

So the question is do we just need to set up a backupstore of 3 TB because the existent fullbackup file is modified or do we have to keep an additional 1 TB for the process because temporary a new full backupfile is build?

[foggy]

With simple retention, there're no temporary files and no additional space is required (unless you perform compact operation).