Probably the ones behind the last couple of half million...

Probably the ones behind the last couple of half million crossings. The last one wouldn't have made it on to this notice, though. The last one would take them below the reporting threshold.
With only five million or so left to go, once they are out of the market it will be interesting to see the effect on price. It's been known in the market that PPT have been selling, meaning there has been an overhang. They represent the last decent sized block of shares outside the founders. Any into wishing to build will need to take PPT out or make it more attractive to remaining shareholders.