I have seen the GUID in the physical_device_name of the backupmediafamily table in SQL Server because of the VSS Writer. What is the number following the GUID? For example, the 28, 29, and 11: {DB7707D5-32D5-4C1A-831C-BF85E274DFAA}29 {9302BBEE-563D-40EB-8FBA-EC1935C2250C}29 {B3CD77DB-8C51-4206-B509-CEC4A571D529}29 {4C76A7E5-DD9F-49C8-B0BD-2D8EBF07E4C5}29 {C2C9435C-552F-4472-B5A0-847F8E8D9AF8}29 {AA45A63B-1675-4D20-B257-507911524428}29 {62822511-203B-4166-8BEB-24BCE4DD4F47}11 {9BB3E977-8738-41B9-901B-86BEEF7AC27D}28 What are they? I've been told they are "the type of backup". Is there a reference document that explains them all?