Global Host CPU - What does that represent?

We have a couple different monitoring systems. Some monitor individual statistics (like BigIQ and SolarWinds), but others are monitoring the SNMP MIB for "Global Host CPU" instead. My main issue is that I cannot find any documentation that relates the Global Host CPU statistics to the multi-CPU statistics being monitored elsewhere. The system monitoring it seems to be using a fairly arbitrary threshold that even the people who chose it cannot explain.

So what does the "Global Host CPU" metric measure and how does that relate to the multiple discrete CPUs being measured by tools like BigIQ and SolarWinds?