This is my first post, been a long time lurker though. I went out to my inverter late in the day (around 4pm) and noticed that P_OK was listed as only 36/40. As I understand it that number is the number of panels the inverter can see. Is it normal for this number to go down as the sun goes down? Or should that number always read 40/40 (in my case)? thanks in advance!