CBT + DDBoost + BBBackups not equal to "almost zero"

Hello,

Just wondering on the space used on a Data Domain when you do several backup of the same server in a short period of time.

Since a while (exactly from the 7 of June) we experiment an increase of the space used on our DD not in relation with data growing.

I discover that on the date where we had a capacity increased we had several manual launch of some backup.

What is "bizarre" is the fact that the capacity used on the DD seems to increase accordingly to the number of backups... (which is "acceptable" in case of traditional file level backup)

If you look at the number of backup version we have for the server "Server one" (as an example) you can see that on the 22 of June we had 5 backup of this server (don't ask me why 5...) and every backup  has a Data Domain copy (which is confirmed by the column AE of the Excel report.

I was expecting that with all CBT + Dedup and whatsoever optimization we will have just few blocks added and not the full disk.

(We are using Networker 9.2.1.4)

Questions:

1) Is CBT an option to be setup on every VM (found an article on that). We are running vSphere 6.5 with vProxy.

2) Even if not activated, a Block Based Backup should do that for you ?

3) Will an Incremental backup not take only modified Blocks ?

3) And what is the role of DDBoost in that "party" ?

Any explanation or answers welcomed because EMC dosen't want to give me a clear explanation how things are really working here...