Merged PR 21183: Clarify AfterFirstUnlock

It does not actually mean "after first unlock".

Author: oldnewthing

windows.security.dataprotection/userdataavailability.md

@@ -17,18 +17,24 @@ Identifies the availability of protected data.
 Data are unprotected when associated with this availability, and are always accessible whether the device is locked or unlocked.
 
 ### -field AfterFirstUnlock:1
-Data protected to this availability are accessible only after the first device unlock, and will continue to stay available thereafter.
+Data protected to this availability are accessible from the time the user signs in until the user signs out or the system is shut down or restarted.
 
 Protecting new data to this availability is always possible.
 
+This is also known as "Level 1" availability.
+
 ### -field WhileUnlocked:2
-Data protected to this availability are only available when the device is unlocked. 
+Data protected to this availability are available only when the user is signed in and the device is unlocked.
 
 Protecting new data to this availability is always possible.
 
+This is also known as "Level 2" availability.
+
 ## -remarks
 
 ## -see-also
 
+[Personal Data Encryption](/windows/security/operating-system-security/data-protection/personal-data-encryption/)
+
 ## -examples