Strange charging behaviour

Hi guys today ive tested charging current on lg g4 with a simple usb tester (drok) and this is what i've found out: max output was 0.6A (isnt the charger max output 1.8A?) when the screen was off and 0A when it was on... Usb cable isn't original because with the original one ive always 0A both screen on and off (i think it has a broken lead). Is this behaviour normal?
View the video i made if im not clear
Thanks

https://youtu.be/AA1djvuEuNI