I have some 380 Watt panels that are rated somewhere around 39 VDC.  An open circuit voltage of 49 volts max.  My POW-LVM3K-24V can handle 30-85 VDC input and 100 Volts open circuit.  So I have put 2 in series to produce 78 VDC under ideal conditions and still under the 100 volts open circuit requirement.  This keeps the wire size down from the panels to the controller.  Each series panel produces 760 Watts.  My controller can handle up to 1600 watts.  So two pairs would produce maximum 1520 watts.  I see a video on another site where their PowerMr 24 volt controller uses a much higher input voltage than 30 – 85 VDC and a higher total wattage allowed.  You might have one of those which would require more panels in series to hit the higher PV voltage.  Probably they changed some of the components that could handle a higher voltage and thus the wire gage internal to the controller is the same.