C9 uses an updated format for .App files.  The upgrade happens when you first open an .App file, and is automatic.  But because the new format makes it impossible to open that .App in a previous version of Clarion, the IDE prompts you to confirm you want the .App converted to the new format.  This is all fine and good, but if you (as many do) have a Solution file that has 20 to -30 or 40+ .App files in it, you would in the past have to confirm upgrading every .App file, whereas C9 offers you this dialog, which allows you to confirm one time for every .App in that Solution.