I want to protect these files every hour, however I want to keep only the last 5 retentions to avoid disk consumption.
I configured the schedule for 5 retentions and enabled the synthetic backup for every day.
But when looking at the backups made I see that it has more than 5 retentions. I know that to do the merge is the synthetic backup schedule but I don't see it happening.
If you want to keep only 5 restore points on the backup repo, you need to disable the daily synthetic full backups. Then it would be a forever forward incremental chain.
With daily synthetic fulls, in your case the old increments can only be deleted as soon the active chain has reached 5 restore points. This will be each day at 5 AM.