Cannot select (default) registry value in System Availability

When setting registry requirements for Distribution rules or Legacy settings in System Availability, it's not possible to select the default value data to be checked (this is the value data that's attached to the key itself, not a value underneath that key) If you export the key, the default value appears as an "@" symbol, like this:
[HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia\Shockwave 10\currentupdateversion]
@="1010011"

To use (default), type the name directly into the name field instead of clicking the button to select, for example

 

Formerly known as TID# 10100913 NOVL105668