AGT.to volume not noteworthy except for the single large 1,669,500sh trade at 12:21. Looks like it was only a few days ago that another large blocks traded, that is, 1,240,000sh at around 09:55 on the 6th of November.
I don't see any reason for concern over a "seller" since there was a "buyer" on other side.
Ring Nebula (2,000 light-years away; WOW! Think about that!)