What to keep?

I'm doing my best to understand the system guide...I have a task scheduled to perform daily, incremental backups and it works. I am going to work on automating moving those out of the destination directory so they don't get overwritten every day. Question is, what is the starting point for those incremental backups, or, what benchmark backup do I need to save initially? Does the backup script or SMT somehow track that for me? Planning on doing a new, full backup every 60 days or so.