Rman backup retention policy and recovery window

This is a place holder for me to understand RMAN backup retention policy and recovery window. I configured daily incrementatl level 1 backup from Monday to Friday, and incremental level 0 backup on Saturday, and retention policy is set to 7 days but when I checked the RMAN backup files on OS level, there are files older than 7 days still existing in the server.  I think this Oracle notes may explain why there are backup files older than the 7 days retention policy existed in the server:

1. Rman backup retention policy [ID 462978.1]
2. Frequently asked questions on Rman backup retention policy [ID 463875.1]
3. NOTE:206862.1 - How does the RMAN Retention Policy Obsolete Incremenatal Backupsets and Archivelog Files
4. NOTE:351455.1 - Oracle Suggested Strategy & Backup Retention
5. NOTE:434345.1 - How Do I Set A Retention Policy For Tape Backups And Disk Backups Differently?
6. NOTE:452529.1 - Recovery catalog for RMAN backup
   

I will further research and modify this post to add more information later.