Great question ;-) ...how do I find out?
However, we are realistic at this price, the monitors will share the 60Hz. But that's enough for my office applications.
The docking station has one of the latest DisplayLink chips in it and theoretically manages 5120x2880 at 60 Hz with a single screen. DisplayPort is the most modern connection ... unless something else is fishy with the laptop's USB or a bad cable or something, it should theoretically work. I only tried 3880 x 1440p, which was no problem.