Applicative CPU activity is a relative percentage figure and is very subjective (*).
It permits to understand how the process or thread is performing with the CPU at one point in time in comparison to the highest process activity moment.
In other words, it gives the application level scope view, opposed to the usual system level scope one (which is objective but also dilutive on high end systems).
Technically, it represents the consumed CPU time divided by the highest CPU peak time observed in a recording session (time ratio adjusted) .
CPU time is the sum of the usr and sys times.
This implies that the applicative CPU activity values computed for one session will oscillate between 0 and 100%, with at least one 100% entry.
(*) If your application is not working much, the applicative CPU activity will be misleading as the 100% could be wrongly interpreted.