Immutability (and block generation) best practice for Azure Storage Account

[DeBi]

Hello, we use B&R v12. Backup for on-prem works fine. We will now use immutability feature and create a copy job with target for Azure Storage account.
The use case is simple. Use a backup copy job to copy all important VMs to an Azure Storage account each Sunday and protect this Storage account with the immutability feature.
In the backup copy job is the immutability set to 7 days (to protect the SA for exact 7 days).
After 7 days the SA was still locked. I found then in the guide the explenation for this - the block generation "feature".
In my case the immutability is not 7 days rather + 1-10 days because the block generation.
But how can then I achieve my use case? How can I schedule a backup copy job with the immutability feature?
What is here best practice?

[veremin]

In the backup copy job is the immutability set to 7 days (to protect the SA for exact 7 days).

Can you point the settings mentioned here? Or the use case you are trying to cover? I'm wondering cause the immutability options are generally presented at repository level, so the approach here might be a bit different. Thanks!

[DeBi]

I mean that regarding Block Generation.
From guide: Veeam will automatically add 1 to 10 days to the immutability expiration date.
How can I use a immutability for 7 days or shorter, if the Block Generation is e. g. 10 days?
Use case: Copy job from repository with the important VMs each 7 days or less.

[veremin]

You can just specify seven days as an immutability period on repository, point a backup copy job to it and don't care about block generation. The data will be undeletable for the required period, plus, you will avoid additional I/O operations and calls, and reduce associated costs as a result. Thanks!

[apolloxm]

Can you explain block generation? per your document, Veeam will automatically add additonal 10 days immutable days. I have configured the immutable days to 2 days in my lab and tried to delete the file from object storage. it said that I only can delete the file after 12days (10days +2 days).