Hi,
An explanation of how we get these final values can be found here: FMOD Engine | White Papers - CPU Performance, and FMOD Studio | Profiling - Reading a Recorded Session.
A great explanation can be found here: getCPUUsage question - #2 by jeff_fmod.
If you are using the default DSP block size with playback of 48khz we expect each system::update is going to take 10ms. If we get a return value of 50% from the core cpu usage we can deduce that each update is actually only taking 5ms.
Hopefully, this will give you enough information to build accurate profiling tools. If there is anything else I can assist with, please let me know.