The Avid Pro Tools HD 10.3.10 R3 hotfix is a maintenance update designed to address specific issues and bugs in the Pro Tools HD software. This update is a incremental release, which means it builds upon the existing version 10.3.10, providing fixes and stability improvements. The "R3" designation indicates that this is the third revision of the 10.3.10 release.
Pro Tools Operating System Compatibility Chart - Knowledge Base Avid Pro Tools HD 10.3.10 R3 hotfix only For Mac
This hotfix is tailored for specific legacy operating systems. The Avid Pro Tools HD 10
Installation notes