https://www.platinum-pen.co.jp/news/11719/
https://www.platinum-pen.co.jp/news/11708/
Source: K. Itoya
Source: Platinum Pen (Location shown is inside K. Itoya store)
I cannot get more discernible detail by zooming in, but could it be that the column of grey-to-black on the advertising poster is showing where Platinum Carbon Black ink's level of blackness sits relative to the new Platinum Chou Kuro ink?