Institutional investors must file a Schedule 13G within 45 days after the calendar year in which the investor holds more than 5% as of the year end or within 10 days after the end of the first month (this month ends tomorrow) in which the person's beneficial ownership exceeds 10%

It would take some work to buy 50MM shares, this kind of volume is crazy too.

They could certainly keep buying during and after the time required to report it.