Ayu's Single and Album record

[orbitalaspect]

(miss)understood was probably counted as 2005 because it was released during the last official Oricon chart for the year, which was, back then, the last week of the old year + the first week of the new year. So, what likely happened is (miss)understood got released a week ahead of the proposed official release, due to the way Oricon tallied release sales at the end of the year, and it was determined, by her #1 in the first week of 2006, that she actually had a #1 album for 2005.