if you search the forum you'll find numerous threads on this.
Noel Borthwick (CTO of cake) states that the CPU meter in sonar is only for the processes of sonar's audio engine as used by the CPU, it is not the same thing as the windows task manager. sonar's CPU meter does not measure ALL CPU usage like windows does, it measures ONLY what Sonar is using.
And the scale may not be the same either.
IMO, it would have been better to have called the meter something other than CPU meter to avoid this confusion.