This graph looks confusing. 400 what?
400 percent. FreeBSD counts in 100 percent per core.
There is only 1 physical, non-HT core on this system.
The more I look at it, the more it seems like the green dot = processes measures literally how many processes are running, whereas the rest of dots (blue, orange, etc.) measure the %CPU load hence the vast difference in magnitude. Is this a plausible theory?
I was mistaken - when you hover over the graph with your mouse pointer you get a legend. It's the number of processes.
The balloon does not show the unit either, but it is now pretty clear what it is.
The unit is processes. The number of them.