Basically the exact meaning of the various channels and their values is vendor specific. So please consult extern sources to be sure what the values mean exactly. The channel id is part of the channel name in PRTG, followed by a ":". After the ":" PRTG states the "typical meaning of the channel", but please be carefull, not all vendors stick to the "typical meaning" but define their own meaning!
Generally each channel reported by the WMI System to the HDD Health Sensor contains information on the state of the channel (e.g.."Might fail soon") . This information is processed by the sensor and PRTG sets the sensor automatically to warning state.
As this is a sensor with only dynamic channels and those are generated at the first scan with what values the scan returns.
At the moment we can't distinguish the values that go in the channels so every channel is generated equally. (UnitKind = Custom and CustomUnit = '#')
You have the opportunity to work with limits which you can enter in the Settings of a sensor or channel.
If you want to have this option included in PRTG, you are welcome to open a Feature Request. Feature Requests are enhancements you desire for the future and are voted by the customers. This means that if your request gets many votes, this increases the prioritisation of our product owners.
Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.