kudos to my colleague Timothy Dewin who wrote an excellent Veeam Backup & Replication Restore Point Simulator.
Keep in mind that this is not official and has not support or garantie that it work correct.
Also deduplication and compression is dependent to the data and is from customer to customer different.
The Default values are OK from my Feeling. If you have Domino DBs this is a bit too low because of Domino own compression.
And don´t forget to select Reverse Incremental if you want max space saving.
Here you can find the tool.