Just a newbie here but please correct me if I'm wrong without jumping all over me. You asked what I think, here it is.
Who ever said each A/S could only be traded ONCE in any 12-day period? I think no one ever said that because it's absurd.
I think the normal back-and-forth action of the market allows shares to be traded several times, and each time it's sold it becomes a "share traded."
Hence, your 1.5 BILLION "shares traded" could easily be 500,000,000 (or, in fact, a lot less). No? Hey, one share traded five times IS five "shares traded," just not five different shares.