Thetype exposes the following members.
Value in bytes representing the amount of additional disk space beyond the current allocation that can be allocated to the folder (or other item) before further allocations will be refused.
Value in bytes representing the amount of space used by this folder/file and possibly a number of other similar folders/files, where the set of "similar" meets at least the criterion that allocating space to any folder/file in the set will count against the GetAvailableBytesAsync. It MUST include the total count including usage derived from sub-items if appropriate. It SHOULD include metadata storage size if metadata storage is counted against the GetAvailableBytesAsync