On 8th day, oldest snapshot get deleted. I am not sure how exactly they handle full/incremental snapshot. Maybe oldest backup automatically become full, new snapshot will only have changes from previous day.
@@zaidilyas7842 every snapshot will take some disk space. How much depends on how much data changed since last snapshot. For snapshot storage, you will be charged $0.05 per GB, this is not size of EC2 disk. Lets say if you have 10 GB disk, you set to have 12 days backup and your daily backup take 1 GB, then your cost will be approx (10 + 12) * $0.05