For 16x400W panels, am I supposed to enter 6400 there? (which would be the theoretic peak DC)
Or something like 6400*eta where eta is efficiency … but how to choose eta then?

Or am I supposed to enter the maximum peak value that was ever produced? For example, on June 19 at 12:30 I observed the highest production thus far (1260Wh between 12:30 and 12:45, so 5040W).

Is this supposed to be AC peak power or DC peak power?

I have Enphase IQ8 microinverters, how do I figure out “rated peak power of the inverter”? Datasheet states 300VA (note, this is VA, not Watts). Is the correct value to enter 16*300=4800 then? That can’t be exactly right either because as stated, the max I ever produced is 5040W which is larger than 4800…