According to RIAJ (Recording Industry Association of Japan)
BLUE BIRD has now hit Platinum, meaning sales over 250,000 copies.
2006年6月度 認定作品
(Recognition work in June, 2006)
邦楽［シングル］
(Japanese music single)
プラチナ BLUE BIRD 浜崎あゆみ 20060621 エイベックス・エンタテインメント
(Platinum BLUE BIRD ayumi hamasaki 20060621 Avex entertainment)
Requirements for the various titles:
http://www.riaj.or.jp/data/others/gold/index.html
BLUE BIRD got プラチナ (puratina)
That means its total sales are over 250,000 copies.
Source (scroll down untill you see BLUE BIRD):
http://www.riaj.or.jp/data/others/gold/200606.html
Credits to
ayumi525 @AYUNITE!
!____!
It's most likely that the RIAJ sales are based on the amount of copies that avex has shipped to the stores rather than the actual amount of sold copies, the single has most probably not yet reached 250,000 on the ORICON charts.