On the P4 display screen, there are some symbols which I would like to know what they mean.

Firstly next to the temperature there is a symbol that looks like ON but it is not clear - this is shown in the first photo below.

Screenshot 2020-04-28 at 15.25.55.jpg

Also directly below that is a - after the pH reading Is there something supposed to show here?

I assume the MY GHL symbol is confirming that I am connected to my GHL? Also, what is the circle mean next to that

This is a second photo once I have connected my heater and the KHD. That ON symbol as changed to just an N? Also, the symbol next to MYGHL is now looking like a crescent moon

Screenshot 2020-04-28 at 15.37.06.jpg


Many thanks