What are the four arrows bottom right (+/-A +/-R) ?

I’ve been trying to work out the size of its Joule Bucket but while staring at the LED blinks I noticed the +R & +A on the LCD and wondered what they meant.

The four quadrants for the power factor: Active power importing and exporting and Reactive power importing and exporting. Unity power factor is along the Active Power axis, zero power factor is along the Reactive Power axis.

It did cross my mind that R could be Reactive, but not that A could be Active (I usually think of real). I found a cute little animation that shows a sweep of the four quadrants, only they label A as P and R as Q. No wonder this can get confusing!

I was taught Real and Imaginary - which makes a lot more sense when you think of it in terms of the j operator and a 90° rotation: start on the positive Real axis and multiply by j and you move 90° anticlockwise onto the positive Imaginary axis; do it twice ( j² ) and it’s the negative Real axis; and three times ( j³ ) and that’s the negative Imaginary axis.