EG4 12000 pv array input question

I'm now looking at using the EG4 12000XP . The question is on the PV array spec it says under (  PV Input Data ) Number of MPPTS 2 . They can have two stings per MPPT and each MPPT 35 amps or 17.5 A per sting if two strings are paralleled to each of the MPPT inputs  ( no problem  understood ). Please understand my solar panels are 395 watts rated at 10a per panel . At 1:00 p.m. I read the solar panel and it read 42.5 vdc at 12.1 A off of one solar panel. So now I have to figure out how many solar panels I can series together on each stings. The spec says " DC Input Voltage 100 - 480Vdc " Great wow how nice. I can really figure out how many to put in a string now right ? Now the spec says also " MPPT operating Voltage  Range 120 - 385 VDC " really ? So now I can use as many in my string as I thought right ? Then it says " Normal MPPT Voltage 320VDC really ? I 'm waiting for but max PV voltage 160vdc now LMAO. So question in figuring out how many solar panels I can put in series do I now go over  480vdc or 385vdc or 320vdc ? I do know that I have to allow 10% for voltage increase . Even tho I measured the voltage during the highest time of the day for my area.   Can someone Please help me to understand what would be the highest VDC per string I would need not to go over ? Thanks so much for any reply !