Explaination regarding measuring device power with the OVR metrics tool

Hi, I am trying to measure the device's power draw in mW while running an XR app. The OVR metrics tool provides:

Battery Current Now: This is the instantaneous current drawn from the battery in milliamps. When I tried logging this metric from the OVR metrics tool I got values that were either 0 or 9999, the value remained at 0 for more than 10 seconds at multiple intervals. May I know if this is fine? and can you help me better understand its output?

The tool also reports Power current which also varies between 0 and around 65. May I know how this metric is different from Battery Current Now? 

Additionally, the tool reports power voltage and power wattage. I referred to this link but the explanation of the metrics was not clear. Can you help me better understand the output of these parameters?

May I know if there is another source or tool through which I can access this information like VrApi logs or through adb commands?

The image below contains the graphs for each parameter for a VR session.