Link the files to iTunes by any of the supported methods. (Open, then Link from Yate or drag the files from iTunes).

You can change the AAC Kind value on the Privacy panel. When the files are saved, iTunes will be modified if the files are linked.

Note:

The ACC Kind field is only applicable for MPEG-4 (AAC) files. This value is extracted from the file external to the metadata store. This field displays the various purchase states displayed by iTunes in the Kind field for a track. It also displays the Mastered for iTunes state if appropriate. If a file was not initially purchased from iTunes, (perhaps it was ripped from another audio format), the value of the field will not change from AAC audio file (or not applicable) if saved with a different value.

Basically, you can only change the value if there was something there initially.

Well, either the "out of bounds" area exists in the file or it does not. If it exists, Yate will allow you to set any AAC Kind and it will be saved. If the storage area does not pre-exist, Yate cannot write it as the overall storage area is undocumented.