Applicative memory activity is a relative percentage figure and is very subjective (*).
It permits to understand how the process or thread is performing with the memory allocation at one point in time in comparison to the highest process memory allocation 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 allocation of bytes in memory divided by the highest allocation peak observed in a recording session (time ratio adjusted).
This implies that the applicative memory 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 memory activity will be misleading as the 100% could be wrongly interpreted.