I have looked into explanations of how Veeam agent works in terms of retention settings on this website, but still something seems wrong with mine.
I have had Veeam Agent for the past 1.5 years and it has always worked perfectly. Just recently though, it was doing a full backup and said my drive ran out of space...this has never happened before in 1.5 years - it has always made space. I looked at the drive and it was FULL of backup files. It hasn't been deleting them.
Looks like at some point you turned on monthly active full. That results in up to 38 restore points (one month + 7 days retention). So everything looks fine for me.
With full backups, there are no merges. That's why.